[v9,04/11] LSM: syscalls for current process attributes
Commit Message
Create a system call lsm_get_self_attr() to provide the security
module maintained attributes of the current process.
Create a system call lsm_set_self_attr() to set a security
module maintained attribute of the current process.
Historically these attributes have been exposed to user space via
entries in procfs under /proc/self/attr.
The attribute value is provided in a lsm_ctx structure. The structure
identifies the size of the attribute, and the attribute value. The format
of the attribute value is defined by the security module. A flags field
is included for LSM specific information. It is currently unused and must
be 0. The total size of the data, including the lsm_ctx structure and any
padding, is maintained as well.
struct lsm_ctx {
__u64 id;
__u64 flags;
__u64 len;
__u64 ctx_len;
__u8 ctx[];
};
Two new LSM hooks are used to interface with the LSMs.
security_getselfattr() collects the lsm_ctx values from the
LSMs that support the hook, accounting for space requirements.
security_setselfattr() identifies which LSM the attribute is
intended for and passes it along.
Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
Documentation/userspace-api/lsm.rst | 15 ++++
include/linux/lsm_hook_defs.h | 4 +
include/linux/lsm_hooks.h | 9 +++
include/linux/security.h | 19 +++++
include/linux/syscalls.h | 5 ++
include/uapi/linux/lsm.h | 36 +++++++++
kernel/sys_ni.c | 4 +
security/Makefile | 1 +
security/lsm_syscalls.c | 55 ++++++++++++++
security/security.c | 110 ++++++++++++++++++++++++++++
10 files changed, 258 insertions(+)
create mode 100644 security/lsm_syscalls.c
Comments
On Fri, Apr 21, 2023 at 10:42:52AM -0700, Casey Schaufler wrote:
> Create a system call lsm_get_self_attr() to provide the security
> module maintained attributes of the current process.
> Create a system call lsm_set_self_attr() to set a security
> module maintained attribute of the current process.
> Historically these attributes have been exposed to user space via
> entries in procfs under /proc/self/attr.
>
> The attribute value is provided in a lsm_ctx structure. The structure
> identifies the size of the attribute, and the attribute value. The format
> of the attribute value is defined by the security module. A flags field
> is included for LSM specific information. It is currently unused and must
> be 0. The total size of the data, including the lsm_ctx structure and any
> padding, is maintained as well.
>
> struct lsm_ctx {
> __u64 id;
> __u64 flags;
> __u64 len;
> __u64 ctx_len;
> __u8 ctx[];
> };
>
> Two new LSM hooks are used to interface with the LSMs.
> security_getselfattr() collects the lsm_ctx values from the
> LSMs that support the hook, accounting for space requirements.
> security_setselfattr() identifies which LSM the attribute is
> intended for and passes it along.
>
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Nits/questions below...
> ---
> Documentation/userspace-api/lsm.rst | 15 ++++
> include/linux/lsm_hook_defs.h | 4 +
> include/linux/lsm_hooks.h | 9 +++
> include/linux/security.h | 19 +++++
> include/linux/syscalls.h | 5 ++
> include/uapi/linux/lsm.h | 36 +++++++++
> kernel/sys_ni.c | 4 +
> security/Makefile | 1 +
> security/lsm_syscalls.c | 55 ++++++++++++++
> security/security.c | 110 ++++++++++++++++++++++++++++
> 10 files changed, 258 insertions(+)
> create mode 100644 security/lsm_syscalls.c
>
> diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
> index 6ddf5506110b..b45e402302b3 100644
> --- a/Documentation/userspace-api/lsm.rst
> +++ b/Documentation/userspace-api/lsm.rst
> @@ -48,6 +48,21 @@ creating socket objects.
> The proc filesystem provides this value in ``/proc/self/attr/sockcreate``.
> This is supported by the SELinux security module.
>
> +Kernel interface
> +================
> +
> +Set a security attribute of the current process
> +--------------------------------------------------
> +
> +.. kernel-doc:: security/lsm_syscalls.c
> + :identifiers: sys_lsm_set_self_attr
> +
> +Get the specified security attributes of the current process
> +--------------------------------------------------
> +
> +.. kernel-doc:: security/lsm_syscalls.c
> + :identifiers: sys_lsm_get_self_attr
> +
> Additional documentation
> ========================
>
> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
> index 094b76dc7164..7177d9554f4a 100644
> --- a/include/linux/lsm_hook_defs.h
> +++ b/include/linux/lsm_hook_defs.h
> @@ -261,6 +261,10 @@ LSM_HOOK(int, 0, sem_semop, struct kern_ipc_perm *perm, struct sembuf *sops,
> LSM_HOOK(int, 0, netlink_send, struct sock *sk, struct sk_buff *skb)
> LSM_HOOK(void, LSM_RET_VOID, d_instantiate, struct dentry *dentry,
> struct inode *inode)
> +LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int __user attr,
> + struct lsm_ctx __user *ctx, size_t *size, u32 __user flags)
> +LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int __user attr,
> + struct lsm_ctx __user *ctx, size_t size, u32 __user flags)
> LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name,
> char **value)
> LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> index 8e6ba0a9896e..ed38ad5eb444 100644
> --- a/include/linux/lsm_hooks.h
> +++ b/include/linux/lsm_hooks.h
> @@ -25,6 +25,7 @@
> #ifndef __LINUX_LSM_HOOKS_H
> #define __LINUX_LSM_HOOKS_H
>
> +#include <uapi/linux/lsm.h>
> #include <linux/security.h>
> #include <linux/init.h>
> #include <linux/rculist.h>
> @@ -503,6 +504,14 @@
> * and writing the xattrs as this hook is merely a filter.
> * @d_instantiate:
> * Fill in @inode security information for a @dentry if allowed.
> + * @getselfattr:
> + * Read attribute @attr for the current process and store it into @ctx.
> + * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
> + * or another negative value otherwise.
> + * @setselfattr:
> + * Set attribute @attr for the current process.
> + * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
> + * or another negative value otherwise.
> * @getprocattr:
> * Read attribute @name for process @p and store it into @value if allowed.
> * Return the length of @value on success, a negative value otherwise.
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 8faed81fc3b4..f7292890b6a2 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -60,6 +60,7 @@ struct fs_parameter;
> enum fs_value_type;
> struct watch;
> struct watch_notification;
> +struct lsm_ctx;
>
> /* Default (no) options for the capable function */
> #define CAP_OPT_NONE 0x0
> @@ -473,6 +474,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
> int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
> unsigned nsops, int alter);
> void security_d_instantiate(struct dentry *dentry, struct inode *inode);
> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
Scalar values aren't marked with "__user": this is for address space
markings (i.e. only on pointers).
> + size_t __user *size, u32 __user flags);
> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> + size_t __user size, u32 __user flags);
> int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
> char **value);
> int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
> @@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
> struct inode *inode)
> { }
>
> +static inline int security_getselfattr(unsigned int __user attr,
> + struct lsm_ctx __user *ctx,
> + size_t __user *size, u32 __user flags)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline int security_setselfattr(unsigned int __user attr,
> + struct lsm_ctx __user *ctx,
> + size_t __user size, u32 __user flags)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> static inline int security_getprocattr(struct task_struct *p, int lsmid,
> const char *name, char **value)
> {
> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
> index 33a0ee3bcb2e..9a94c31bf6b6 100644
> --- a/include/linux/syscalls.h
> +++ b/include/linux/syscalls.h
> @@ -71,6 +71,7 @@ struct clone_args;
> struct open_how;
> struct mount_attr;
> struct landlock_ruleset_attr;
> +struct lsm_ctx;
> enum landlock_rule_type;
>
> #include <linux/types.h>
> @@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
> asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
> unsigned long home_node,
> unsigned long flags);
> +asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> + size_t *size, __u32 flags);
> +asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
> + size_t size, __u32 flags);
It'd be nice if these syscalls could stick to the "verionable" syscall
conventions (like openat2) as much as possible. Is "flags" needed here
if we this is only ever going to be 1 LSM at a time?
>
> /*
> * Architecture-specific system calls
> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
> index f27c9a9cc376..eeda59a77c02 100644
> --- a/include/uapi/linux/lsm.h
> +++ b/include/uapi/linux/lsm.h
> @@ -9,6 +9,36 @@
> #ifndef _UAPI_LINUX_LSM_H
> #define _UAPI_LINUX_LSM_H
>
> +#include <linux/types.h>
> +#include <linux/unistd.h>
> +
> +/**
> + * struct lsm_ctx - LSM context information
> + * @id: the LSM id number, see LSM_ID_XXX
> + * @flags: LSM specific flags
> + * @len: length of the lsm_ctx struct, @ctx and any other data or padding
> + * @ctx_len: the size of @ctx
> + * @ctx: the LSM context value
> + *
> + * The @len field MUST be equal to the size of the lsm_ctx struct
> + * plus any additional padding and/or data placed after @ctx.
> + *
> + * In all cases @ctx_len MUST be equal to the length of @ctx.
> + * If @ctx is a string value it should be nul terminated with
> + * @ctx_len equal to `strlen(@ctx) + 1`. Binary values are
> + * supported.
> + *
> + * The @flags and @ctx fields SHOULD only be interpreted by the
> + * LSM specified by @id; they MUST be set to zero/0 when not used.
> + */
> +struct lsm_ctx {
> + __u64 id;
> + __u64 flags;
> + __u64 len;
> + __u64 ctx_len;
> + __u8 ctx[];
> +};
> +
> /*
> * ID tokens to identify Linux Security Modules (LSMs)
> *
> @@ -51,4 +81,10 @@
> #define LSM_ATTR_PREV 104
> #define LSM_ATTR_SOCKCREATE 105
>
> +/*
> + * LSM_FLAG_XXX definitions identify special handling instructions
> + * for the API.
> + */
> +#define LSM_FLAG_SINGLE 0x0001
> +
> #endif /* _UAPI_LINUX_LSM_H */
> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
> index 860b2dcf3ac4..d03c78ef1562 100644
> --- a/kernel/sys_ni.c
> +++ b/kernel/sys_ni.c
> @@ -262,6 +262,10 @@ COND_SYSCALL_COMPAT(recvmsg);
> /* mm/nommu.c, also with MMU */
> COND_SYSCALL(mremap);
>
> +/* security/lsm_syscalls.c */
> +COND_SYSCALL(lsm_get_self_attr);
> +COND_SYSCALL(lsm_set_self_attr);
> +
> /* security/keys/keyctl.c */
> COND_SYSCALL(add_key);
> COND_SYSCALL(request_key);
> diff --git a/security/Makefile b/security/Makefile
> index 18121f8f85cd..59f238490665 100644
> --- a/security/Makefile
> +++ b/security/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_KEYS) += keys/
>
> # always enable default capabilities
> obj-y += commoncap.o
> +obj-$(CONFIG_SECURITY) += lsm_syscalls.o
> obj-$(CONFIG_MMU) += min_addr.o
>
> # Object file lists
> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
> new file mode 100644
> index 000000000000..feee31600219
> --- /dev/null
> +++ b/security/lsm_syscalls.c
> @@ -0,0 +1,55 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * System calls implementing the Linux Security Module API.
> + *
> + * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
> + * Copyright (C) 2022 Intel Corporation
> + */
> +
> +#include <asm/current.h>
> +#include <linux/compiler_types.h>
> +#include <linux/err.h>
> +#include <linux/errno.h>
> +#include <linux/security.h>
> +#include <linux/stddef.h>
> +#include <linux/syscalls.h>
> +#include <linux/types.h>
> +#include <linux/lsm_hooks.h>
> +#include <uapi/linux/lsm.h>
> +
> +/**
> + * sys_lsm_set_self_attr - Set current task's security module attribute
> + * @attr: which attribute to set
> + * @ctx: the LSM contexts
> + * @size: size of @ctx
> + * @flags: reserved for future use
> + *
> + * Sets the calling task's LSM context. On success this function
> + * returns 0. If the attribute specified cannot be set a negative
> + * value indicating the reason for the error is returned.
> + */
> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> + ctx, size_t __user, size, u32, flags)
> +{
> + return security_setselfattr(attr, ctx, size, flags);
> +}
> +
> +/**
> + * sys_lsm_get_self_attr - Return current task's security module attributes
> + * @attr: which attribute to set
> + * @ctx: the LSM contexts
> + * @size: size of @ctx, updated on return
> + * @flags: reserved for future use
> + *
> + * Returns the calling task's LSM contexts. On success this
> + * function returns the number of @ctx array elements. This value
> + * may be zero if there are no LSM contexts assigned. If @size is
> + * insufficient to contain the return data -E2BIG is returned and
> + * @size is set to the minimum required size. In all other cases
> + * a negative value indicating the error is returned.
> + */
> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
> + ctx, size_t __user *, size, u32, flags)
> +{
> + return security_getselfattr(attr, ctx, size, flags);
> +}
> diff --git a/security/security.c b/security/security.c
> index 38ca0e646cac..bc3f166b4bff 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -2167,6 +2167,116 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
> }
> EXPORT_SYMBOL(security_d_instantiate);
>
> +/**
> + * security_getselfattr - Read an LSM attribute of the current process.
> + * @attr: which attribute to return
> + * @ctx: the user-space destination for the information, or NULL
> + * @size: the size of space available to receive the data
> + * @flags: special handling options. LSM_FLAG_SINGLE indicates that only
> + * attributes associated with the LSM identified in the passed @ctx be
> + * reported
> + *
> + * Returns the number of attributes found on success, negative value
> + * on error. @size is reset to the total size of the data.
> + * If @size is insufficient to contain the data -E2BIG is returned.
> + */
> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> + size_t __user *size, u32 __user flags)
> +{
> + struct security_hook_list *hp;
> + struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, };
> + u8 __user *base = (u8 __user *)ctx;
> + size_t total = 0;
> + size_t entrysize;
> + size_t left;
> + bool toobig = false;
> + int count = 0;
> + int rc;
> +
> + if (attr == 0)
> + return -EINVAL;
> + if (size == NULL)
> + return -EINVAL;
> + if (get_user(left, size))
> + return -EFAULT;
> +
> + if ((flags & LSM_FLAG_SINGLE) == LSM_FLAG_SINGLE) {
> + if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
> + return -EFAULT;
> + if (lctx.id == LSM_ID_UNDEF)
> + return -EINVAL;
> + } else if (flags) {
> + return -EINVAL;
> + }
Can this use copy_struct_from_user() instead? It would be nice to reuse
that here.
> +
> + hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
> + if (lctx.id != LSM_ID_UNDEF && lctx.id != hp->lsmid->id)
> + continue;
> + entrysize = left;
> + if (base)
> + ctx = (struct lsm_ctx __user *)(base + total);
> + rc = hp->hook.getselfattr(attr, ctx, &entrysize, flags);
> + if (rc == -EOPNOTSUPP) {
> + rc = 0;
> + continue;
> + }
> + if (rc == -E2BIG) {
> + toobig = true;
> + left = 0;
> + continue;
> + }
> + if (rc < 0)
> + return rc;
> +
> + left -= entrysize;
> + total += entrysize;
> + count += rc;
> + }
> + if (put_user(total, size))
> + return -EFAULT;
> + if (toobig)
> + return -E2BIG;
> + if (count == 0)
> + return LSM_RET_DEFAULT(getselfattr);
> + return count;
> +}
> +
> +/**
> + * security_setselfattr - Set an LSM attribute on the current process.
> + * @attr: which attribute to set
> + * @ctx: the user-space source for the information
> + * @size: the size of the data
> + * @flags: reserved for future use, must be 0
> + *
> + * Set an LSM attribute for the current process. The LSM, attribute
> + * and new value are included in @ctx.
> + *
> + * Returns 0 on success, -EINVAL if the input is inconsistent, -EFAULT
> + * if the user buffer is inaccessible or an LSM specific failure.
> + */
> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> + size_t __user size, u32 __user flags)
> +{
> + struct security_hook_list *hp;
> + struct lsm_ctx lctx;
> +
> + if (flags)
> + return -EINVAL;
> + if (size < sizeof(*ctx))
> + return -EINVAL;
> + if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
> + return -EFAULT;
> + if (size < lctx.len || size < lctx.ctx_len + sizeof(ctx) ||
> + lctx.len < lctx.ctx_len + sizeof(ctx))
> + return -EINVAL;
> +
> + hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
> + if ((hp->lsmid->id) == lctx.id)
> + return hp->hook.setselfattr(attr, ctx, size, flags);
> +
> + return LSM_RET_DEFAULT(setselfattr);
> +}
> +
> int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
> char **value)
> {
> --
> 2.39.2
>
Hi Casey,
kernel test robot noticed the following build warnings:
[auto build test WARNING on tip/perf/core]
[also build test WARNING on acme/perf/core shuah-kselftest/next shuah-kselftest/fixes linus/master v6.3-rc7]
[cannot apply to next-20230421]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230422-024331
base: tip/perf/core
patch link: https://lore.kernel.org/r/20230421174259.2458-5-casey%40schaufler-ca.com
patch subject: [PATCH v9 04/11] LSM: syscalls for current process attributes
config: mips-randconfig-s051-20230421 (https://download.01.org/0day-ci/archive/20230422/202304222142.YHgqLhGF-lkp@intel.com/config)
compiler: mips64el-linux-gcc (GCC) 12.1.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# apt-get install sparse
# sparse version: v0.6.4-39-gce1a6720-dirty
# https://github.com/intel-lab-lkp/linux/commit/78ea54cc31d7bd9e5a5c7fe8cf34fba9516fde95
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230422-024331
git checkout 78ea54cc31d7bd9e5a5c7fe8cf34fba9516fde95
# save the config file
mkdir build_dir && cp config build_dir/.config
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=mips olddefconfig
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=mips SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304222142.YHgqLhGF-lkp@intel.com/
sparse warnings: (new ones prefixed by >>)
>> security/lsm_syscalls.c:34:48: sparse: sparse: dereference of noderef expression
--
security/security.c:406:25: sparse: sparse: cast removes address space '__rcu' of expression
>> security/security.c:2196:13: sparse: sparse: dereference of noderef expression
security/security.c:2203:14: sparse: sparse: dereference of noderef expression
security/security.c:2208:20: sparse: sparse: dereference of noderef expression
security/security.c:2218:43: sparse: sparse: dereference of noderef expression
security/security.c:2218:66: sparse: sparse: dereference of noderef expression
security/security.c:2263:13: sparse: sparse: dereference of noderef expression
security/security.c:2265:13: sparse: sparse: dereference of noderef expression
security/security.c:2269:13: sparse: sparse: dereference of noderef expression
security/security.c:2269:32: sparse: sparse: dereference of noderef expression
security/security.c:2275:53: sparse: sparse: dereference of noderef expression
security/security.c:2275:64: sparse: sparse: dereference of noderef expression
security/security.c:2275:70: sparse: sparse: dereference of noderef expression
vim +34 security/lsm_syscalls.c
19
20 /**
21 * sys_lsm_set_self_attr - Set current task's security module attribute
22 * @attr: which attribute to set
23 * @ctx: the LSM contexts
24 * @size: size of @ctx
25 * @flags: reserved for future use
26 *
27 * Sets the calling task's LSM context. On success this function
28 * returns 0. If the attribute specified cannot be set a negative
29 * value indicating the reason for the error is returned.
30 */
31 SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
32 ctx, size_t __user, size, u32, flags)
33 {
> 34 return security_setselfattr(attr, ctx, size, flags);
35 }
36
Hi Casey,
kernel test robot noticed the following build warnings:
[auto build test WARNING on tip/perf/core]
[also build test WARNING on acme/perf/core shuah-kselftest/next shuah-kselftest/fixes linus/master v6.3-rc7]
[cannot apply to next-20230421]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230422-024331
base: tip/perf/core
patch link: https://lore.kernel.org/r/20230421174259.2458-5-casey%40schaufler-ca.com
patch subject: [PATCH v9 04/11] LSM: syscalls for current process attributes
reproduce:
# https://github.com/intel-lab-lkp/linux/commit/78ea54cc31d7bd9e5a5c7fe8cf34fba9516fde95
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Casey-Schaufler/LSM-Maintain-a-table-of-LSM-attribute-data/20230422-024331
git checkout 78ea54cc31d7bd9e5a5c7fe8cf34fba9516fde95
make menuconfig
# enable CONFIG_COMPILE_TEST, CONFIG_WARN_MISSING_DOCUMENTS, CONFIG_WARN_ABI_ERRORS
make htmldocs
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304230040.qjeOFf1q-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> Documentation/userspace-api/lsm.rst:61: WARNING: Title underline too short.
vim +61 Documentation/userspace-api/lsm.rst
56
57 .. kernel-doc:: security/lsm_syscalls.c
58 :identifiers: sys_lsm_set_self_attr
59
60 Get the specified security attributes of the current process
> 61 --------------------------------------------------
62
On 4/21/2023 12:36 PM, Kees Cook wrote:
> On Fri, Apr 21, 2023 at 10:42:52AM -0700, Casey Schaufler wrote:
>> Create a system call lsm_get_self_attr() to provide the security
>> module maintained attributes of the current process.
>> Create a system call lsm_set_self_attr() to set a security
>> module maintained attribute of the current process.
>> Historically these attributes have been exposed to user space via
>> entries in procfs under /proc/self/attr.
>>
>> The attribute value is provided in a lsm_ctx structure. The structure
>> identifies the size of the attribute, and the attribute value. The format
>> of the attribute value is defined by the security module. A flags field
>> is included for LSM specific information. It is currently unused and must
>> be 0. The total size of the data, including the lsm_ctx structure and any
>> padding, is maintained as well.
>>
>> struct lsm_ctx {
>> __u64 id;
>> __u64 flags;
>> __u64 len;
>> __u64 ctx_len;
>> __u8 ctx[];
>> };
>>
>> Two new LSM hooks are used to interface with the LSMs.
>> security_getselfattr() collects the lsm_ctx values from the
>> LSMs that support the hook, accounting for space requirements.
>> security_setselfattr() identifies which LSM the attribute is
>> intended for and passes it along.
>>
>> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
>
> Nits/questions below...
>
>> ---
>> Documentation/userspace-api/lsm.rst | 15 ++++
>> include/linux/lsm_hook_defs.h | 4 +
>> include/linux/lsm_hooks.h | 9 +++
>> include/linux/security.h | 19 +++++
>> include/linux/syscalls.h | 5 ++
>> include/uapi/linux/lsm.h | 36 +++++++++
>> kernel/sys_ni.c | 4 +
>> security/Makefile | 1 +
>> security/lsm_syscalls.c | 55 ++++++++++++++
>> security/security.c | 110 ++++++++++++++++++++++++++++
>> 10 files changed, 258 insertions(+)
>> create mode 100644 security/lsm_syscalls.c
>>
>> diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst
>> index 6ddf5506110b..b45e402302b3 100644
>> --- a/Documentation/userspace-api/lsm.rst
>> +++ b/Documentation/userspace-api/lsm.rst
>> @@ -48,6 +48,21 @@ creating socket objects.
>> The proc filesystem provides this value in ``/proc/self/attr/sockcreate``.
>> This is supported by the SELinux security module.
>>
>> +Kernel interface
>> +================
>> +
>> +Set a security attribute of the current process
>> +--------------------------------------------------
>> +
>> +.. kernel-doc:: security/lsm_syscalls.c
>> + :identifiers: sys_lsm_set_self_attr
>> +
>> +Get the specified security attributes of the current process
>> +--------------------------------------------------
>> +
>> +.. kernel-doc:: security/lsm_syscalls.c
>> + :identifiers: sys_lsm_get_self_attr
>> +
>> Additional documentation
>> ========================
>>
>> diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
>> index 094b76dc7164..7177d9554f4a 100644
>> --- a/include/linux/lsm_hook_defs.h
>> +++ b/include/linux/lsm_hook_defs.h
>> @@ -261,6 +261,10 @@ LSM_HOOK(int, 0, sem_semop, struct kern_ipc_perm *perm, struct sembuf *sops,
>> LSM_HOOK(int, 0, netlink_send, struct sock *sk, struct sk_buff *skb)
>> LSM_HOOK(void, LSM_RET_VOID, d_instantiate, struct dentry *dentry,
>> struct inode *inode)
>> +LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int __user attr,
>> + struct lsm_ctx __user *ctx, size_t *size, u32 __user flags)
>> +LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int __user attr,
>> + struct lsm_ctx __user *ctx, size_t size, u32 __user flags)
>> LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name,
>> char **value)
>> LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
>> diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
>> index 8e6ba0a9896e..ed38ad5eb444 100644
>> --- a/include/linux/lsm_hooks.h
>> +++ b/include/linux/lsm_hooks.h
>> @@ -25,6 +25,7 @@
>> #ifndef __LINUX_LSM_HOOKS_H
>> #define __LINUX_LSM_HOOKS_H
>>
>> +#include <uapi/linux/lsm.h>
>> #include <linux/security.h>
>> #include <linux/init.h>
>> #include <linux/rculist.h>
>> @@ -503,6 +504,14 @@
>> * and writing the xattrs as this hook is merely a filter.
>> * @d_instantiate:
>> * Fill in @inode security information for a @dentry if allowed.
>> + * @getselfattr:
>> + * Read attribute @attr for the current process and store it into @ctx.
>> + * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
>> + * or another negative value otherwise.
>> + * @setselfattr:
>> + * Set attribute @attr for the current process.
>> + * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
>> + * or another negative value otherwise.
>> * @getprocattr:
>> * Read attribute @name for process @p and store it into @value if allowed.
>> * Return the length of @value on success, a negative value otherwise.
>> diff --git a/include/linux/security.h b/include/linux/security.h
>> index 8faed81fc3b4..f7292890b6a2 100644
>> --- a/include/linux/security.h
>> +++ b/include/linux/security.h
>> @@ -60,6 +60,7 @@ struct fs_parameter;
>> enum fs_value_type;
>> struct watch;
>> struct watch_notification;
>> +struct lsm_ctx;
>>
>> /* Default (no) options for the capable function */
>> #define CAP_OPT_NONE 0x0
>> @@ -473,6 +474,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
>> int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
>> unsigned nsops, int alter);
>> void security_d_instantiate(struct dentry *dentry, struct inode *inode);
>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
> Scalar values aren't marked with "__user": this is for address space
> markings (i.e. only on pointers).
>
>> + size_t __user *size, u32 __user flags);
>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> + size_t __user size, u32 __user flags);
>> int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
>> char **value);
>> int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
>> @@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
>> struct inode *inode)
>> { }
>>
>> +static inline int security_getselfattr(unsigned int __user attr,
>> + struct lsm_ctx __user *ctx,
>> + size_t __user *size, u32 __user flags)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +
>> +static inline int security_setselfattr(unsigned int __user attr,
>> + struct lsm_ctx __user *ctx,
>> + size_t __user size, u32 __user flags)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +
>> static inline int security_getprocattr(struct task_struct *p, int lsmid,
>> const char *name, char **value)
>> {
>> diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
>> index 33a0ee3bcb2e..9a94c31bf6b6 100644
>> --- a/include/linux/syscalls.h
>> +++ b/include/linux/syscalls.h
>> @@ -71,6 +71,7 @@ struct clone_args;
>> struct open_how;
>> struct mount_attr;
>> struct landlock_ruleset_attr;
>> +struct lsm_ctx;
>> enum landlock_rule_type;
>>
>> #include <linux/types.h>
>> @@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
>> asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
>> unsigned long home_node,
>> unsigned long flags);
>> +asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>> + size_t *size, __u32 flags);
>> +asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
>> + size_t size, __u32 flags);
> It'd be nice if these syscalls could stick to the "verionable" syscall
> conventions (like openat2) as much as possible. Is "flags" needed here
> if we this is only ever going to be 1 LSM at a time?
Consider a future LSM that allows you to edit an attribute. Viable flags
might be LSM_FLAG_ADD_TO_ATTRIBUTE, LSM_FLAG_DELETE_FROM_ATTRIBUTE,
LSM_FLAG_REPLACE_ATTRIBUTE, LSM_FLAG_SET_ONLY_IF_EMPTY, and so forth.
This could be useful in an Bell & LaPadula implementation, adding or
removing categories on the fly. OK, no B&L would really allow that, but
The point should be clear.
>>
>> /*
>> * Architecture-specific system calls
>> diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
>> index f27c9a9cc376..eeda59a77c02 100644
>> --- a/include/uapi/linux/lsm.h
>> +++ b/include/uapi/linux/lsm.h
>> @@ -9,6 +9,36 @@
>> #ifndef _UAPI_LINUX_LSM_H
>> #define _UAPI_LINUX_LSM_H
>>
>> +#include <linux/types.h>
>> +#include <linux/unistd.h>
>> +
>> +/**
>> + * struct lsm_ctx - LSM context information
>> + * @id: the LSM id number, see LSM_ID_XXX
>> + * @flags: LSM specific flags
>> + * @len: length of the lsm_ctx struct, @ctx and any other data or padding
>> + * @ctx_len: the size of @ctx
>> + * @ctx: the LSM context value
>> + *
>> + * The @len field MUST be equal to the size of the lsm_ctx struct
>> + * plus any additional padding and/or data placed after @ctx.
>> + *
>> + * In all cases @ctx_len MUST be equal to the length of @ctx.
>> + * If @ctx is a string value it should be nul terminated with
>> + * @ctx_len equal to `strlen(@ctx) + 1`. Binary values are
>> + * supported.
>> + *
>> + * The @flags and @ctx fields SHOULD only be interpreted by the
>> + * LSM specified by @id; they MUST be set to zero/0 when not used.
>> + */
>> +struct lsm_ctx {
>> + __u64 id;
>> + __u64 flags;
>> + __u64 len;
>> + __u64 ctx_len;
>> + __u8 ctx[];
>> +};
>> +
>> /*
>> * ID tokens to identify Linux Security Modules (LSMs)
>> *
>> @@ -51,4 +81,10 @@
>> #define LSM_ATTR_PREV 104
>> #define LSM_ATTR_SOCKCREATE 105
>>
>> +/*
>> + * LSM_FLAG_XXX definitions identify special handling instructions
>> + * for the API.
>> + */
>> +#define LSM_FLAG_SINGLE 0x0001
>> +
>> #endif /* _UAPI_LINUX_LSM_H */
>> diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
>> index 860b2dcf3ac4..d03c78ef1562 100644
>> --- a/kernel/sys_ni.c
>> +++ b/kernel/sys_ni.c
>> @@ -262,6 +262,10 @@ COND_SYSCALL_COMPAT(recvmsg);
>> /* mm/nommu.c, also with MMU */
>> COND_SYSCALL(mremap);
>>
>> +/* security/lsm_syscalls.c */
>> +COND_SYSCALL(lsm_get_self_attr);
>> +COND_SYSCALL(lsm_set_self_attr);
>> +
>> /* security/keys/keyctl.c */
>> COND_SYSCALL(add_key);
>> COND_SYSCALL(request_key);
>> diff --git a/security/Makefile b/security/Makefile
>> index 18121f8f85cd..59f238490665 100644
>> --- a/security/Makefile
>> +++ b/security/Makefile
>> @@ -7,6 +7,7 @@ obj-$(CONFIG_KEYS) += keys/
>>
>> # always enable default capabilities
>> obj-y += commoncap.o
>> +obj-$(CONFIG_SECURITY) += lsm_syscalls.o
>> obj-$(CONFIG_MMU) += min_addr.o
>>
>> # Object file lists
>> diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c
>> new file mode 100644
>> index 000000000000..feee31600219
>> --- /dev/null
>> +++ b/security/lsm_syscalls.c
>> @@ -0,0 +1,55 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * System calls implementing the Linux Security Module API.
>> + *
>> + * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
>> + * Copyright (C) 2022 Intel Corporation
>> + */
>> +
>> +#include <asm/current.h>
>> +#include <linux/compiler_types.h>
>> +#include <linux/err.h>
>> +#include <linux/errno.h>
>> +#include <linux/security.h>
>> +#include <linux/stddef.h>
>> +#include <linux/syscalls.h>
>> +#include <linux/types.h>
>> +#include <linux/lsm_hooks.h>
>> +#include <uapi/linux/lsm.h>
>> +
>> +/**
>> + * sys_lsm_set_self_attr - Set current task's security module attribute
>> + * @attr: which attribute to set
>> + * @ctx: the LSM contexts
>> + * @size: size of @ctx
>> + * @flags: reserved for future use
>> + *
>> + * Sets the calling task's LSM context. On success this function
>> + * returns 0. If the attribute specified cannot be set a negative
>> + * value indicating the reason for the error is returned.
>> + */
>> +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
>> + ctx, size_t __user, size, u32, flags)
>> +{
>> + return security_setselfattr(attr, ctx, size, flags);
>> +}
>> +
>> +/**
>> + * sys_lsm_get_self_attr - Return current task's security module attributes
>> + * @attr: which attribute to set
>> + * @ctx: the LSM contexts
>> + * @size: size of @ctx, updated on return
>> + * @flags: reserved for future use
>> + *
>> + * Returns the calling task's LSM contexts. On success this
>> + * function returns the number of @ctx array elements. This value
>> + * may be zero if there are no LSM contexts assigned. If @size is
>> + * insufficient to contain the return data -E2BIG is returned and
>> + * @size is set to the minimum required size. In all other cases
>> + * a negative value indicating the error is returned.
>> + */
>> +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
>> + ctx, size_t __user *, size, u32, flags)
>> +{
>> + return security_getselfattr(attr, ctx, size, flags);
>> +}
>> diff --git a/security/security.c b/security/security.c
>> index 38ca0e646cac..bc3f166b4bff 100644
>> --- a/security/security.c
>> +++ b/security/security.c
>> @@ -2167,6 +2167,116 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
>> }
>> EXPORT_SYMBOL(security_d_instantiate);
>>
>> +/**
>> + * security_getselfattr - Read an LSM attribute of the current process.
>> + * @attr: which attribute to return
>> + * @ctx: the user-space destination for the information, or NULL
>> + * @size: the size of space available to receive the data
>> + * @flags: special handling options. LSM_FLAG_SINGLE indicates that only
>> + * attributes associated with the LSM identified in the passed @ctx be
>> + * reported
>> + *
>> + * Returns the number of attributes found on success, negative value
>> + * on error. @size is reset to the total size of the data.
>> + * If @size is insufficient to contain the data -E2BIG is returned.
>> + */
>> +int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> + size_t __user *size, u32 __user flags)
>> +{
>> + struct security_hook_list *hp;
>> + struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, };
>> + u8 __user *base = (u8 __user *)ctx;
>> + size_t total = 0;
>> + size_t entrysize;
>> + size_t left;
>> + bool toobig = false;
>> + int count = 0;
>> + int rc;
>> +
>> + if (attr == 0)
>> + return -EINVAL;
>> + if (size == NULL)
>> + return -EINVAL;
>> + if (get_user(left, size))
>> + return -EFAULT;
>> +
>> + if ((flags & LSM_FLAG_SINGLE) == LSM_FLAG_SINGLE) {
>> + if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>> + return -EFAULT;
>> + if (lctx.id == LSM_ID_UNDEF)
>> + return -EINVAL;
>> + } else if (flags) {
>> + return -EINVAL;
>> + }
> Can this use copy_struct_from_user() instead? It would be nice to reuse
> that here.
Yes. Missed that one.
>
>> +
>> + hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
>> + if (lctx.id != LSM_ID_UNDEF && lctx.id != hp->lsmid->id)
>> + continue;
>> + entrysize = left;
>> + if (base)
>> + ctx = (struct lsm_ctx __user *)(base + total);
>> + rc = hp->hook.getselfattr(attr, ctx, &entrysize, flags);
>> + if (rc == -EOPNOTSUPP) {
>> + rc = 0;
>> + continue;
>> + }
>> + if (rc == -E2BIG) {
>> + toobig = true;
>> + left = 0;
>> + continue;
>> + }
>> + if (rc < 0)
>> + return rc;
>> +
>> + left -= entrysize;
>> + total += entrysize;
>> + count += rc;
>> + }
>> + if (put_user(total, size))
>> + return -EFAULT;
>> + if (toobig)
>> + return -E2BIG;
>> + if (count == 0)
>> + return LSM_RET_DEFAULT(getselfattr);
>> + return count;
>> +}
>> +
>> +/**
>> + * security_setselfattr - Set an LSM attribute on the current process.
>> + * @attr: which attribute to set
>> + * @ctx: the user-space source for the information
>> + * @size: the size of the data
>> + * @flags: reserved for future use, must be 0
>> + *
>> + * Set an LSM attribute for the current process. The LSM, attribute
>> + * and new value are included in @ctx.
>> + *
>> + * Returns 0 on success, -EINVAL if the input is inconsistent, -EFAULT
>> + * if the user buffer is inaccessible or an LSM specific failure.
>> + */
>> +int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
>> + size_t __user size, u32 __user flags)
>> +{
>> + struct security_hook_list *hp;
>> + struct lsm_ctx lctx;
>> +
>> + if (flags)
>> + return -EINVAL;
>> + if (size < sizeof(*ctx))
>> + return -EINVAL;
>> + if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
>> + return -EFAULT;
>> + if (size < lctx.len || size < lctx.ctx_len + sizeof(ctx) ||
>> + lctx.len < lctx.ctx_len + sizeof(ctx))
>> + return -EINVAL;
>> +
>> + hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
>> + if ((hp->lsmid->id) == lctx.id)
>> + return hp->hook.setselfattr(attr, ctx, size, flags);
>> +
>> + return LSM_RET_DEFAULT(setselfattr);
>> +}
>> +
>> int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
>> char **value)
>> {
>> --
>> 2.39.2
>>
@@ -48,6 +48,21 @@ creating socket objects.
The proc filesystem provides this value in ``/proc/self/attr/sockcreate``.
This is supported by the SELinux security module.
+Kernel interface
+================
+
+Set a security attribute of the current process
+--------------------------------------------------
+
+.. kernel-doc:: security/lsm_syscalls.c
+ :identifiers: sys_lsm_set_self_attr
+
+Get the specified security attributes of the current process
+--------------------------------------------------
+
+.. kernel-doc:: security/lsm_syscalls.c
+ :identifiers: sys_lsm_get_self_attr
+
Additional documentation
========================
@@ -261,6 +261,10 @@ LSM_HOOK(int, 0, sem_semop, struct kern_ipc_perm *perm, struct sembuf *sops,
LSM_HOOK(int, 0, netlink_send, struct sock *sk, struct sk_buff *skb)
LSM_HOOK(void, LSM_RET_VOID, d_instantiate, struct dentry *dentry,
struct inode *inode)
+LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int __user attr,
+ struct lsm_ctx __user *ctx, size_t *size, u32 __user flags)
+LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int __user attr,
+ struct lsm_ctx __user *ctx, size_t size, u32 __user flags)
LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name,
char **value)
LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size)
@@ -25,6 +25,7 @@
#ifndef __LINUX_LSM_HOOKS_H
#define __LINUX_LSM_HOOKS_H
+#include <uapi/linux/lsm.h>
#include <linux/security.h>
#include <linux/init.h>
#include <linux/rculist.h>
@@ -503,6 +504,14 @@
* and writing the xattrs as this hook is merely a filter.
* @d_instantiate:
* Fill in @inode security information for a @dentry if allowed.
+ * @getselfattr:
+ * Read attribute @attr for the current process and store it into @ctx.
+ * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
+ * or another negative value otherwise.
+ * @setselfattr:
+ * Set attribute @attr for the current process.
+ * Return 0 on success, -EOPNOTSUPP if the attribute is not supported,
+ * or another negative value otherwise.
* @getprocattr:
* Read attribute @name for process @p and store it into @value if allowed.
* Return the length of @value on success, a negative value otherwise.
@@ -60,6 +60,7 @@ struct fs_parameter;
enum fs_value_type;
struct watch;
struct watch_notification;
+struct lsm_ctx;
/* Default (no) options for the capable function */
#define CAP_OPT_NONE 0x0
@@ -473,6 +474,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd);
int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops,
unsigned nsops, int alter);
void security_d_instantiate(struct dentry *dentry, struct inode *inode);
+int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+ size_t __user *size, u32 __user flags);
+int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+ size_t __user size, u32 __user flags);
int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
char **value);
int security_setprocattr(int lsmid, const char *name, void *value, size_t size);
@@ -1343,6 +1348,20 @@ static inline void security_d_instantiate(struct dentry *dentry,
struct inode *inode)
{ }
+static inline int security_getselfattr(unsigned int __user attr,
+ struct lsm_ctx __user *ctx,
+ size_t __user *size, u32 __user flags)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int security_setselfattr(unsigned int __user attr,
+ struct lsm_ctx __user *ctx,
+ size_t __user size, u32 __user flags)
+{
+ return -EOPNOTSUPP;
+}
+
static inline int security_getprocattr(struct task_struct *p, int lsmid,
const char *name, char **value)
{
@@ -71,6 +71,7 @@ struct clone_args;
struct open_how;
struct mount_attr;
struct landlock_ruleset_attr;
+struct lsm_ctx;
enum landlock_rule_type;
#include <linux/types.h>
@@ -1058,6 +1059,10 @@ asmlinkage long sys_memfd_secret(unsigned int flags);
asmlinkage long sys_set_mempolicy_home_node(unsigned long start, unsigned long len,
unsigned long home_node,
unsigned long flags);
+asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+ size_t *size, __u32 flags);
+asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx,
+ size_t size, __u32 flags);
/*
* Architecture-specific system calls
@@ -9,6 +9,36 @@
#ifndef _UAPI_LINUX_LSM_H
#define _UAPI_LINUX_LSM_H
+#include <linux/types.h>
+#include <linux/unistd.h>
+
+/**
+ * struct lsm_ctx - LSM context information
+ * @id: the LSM id number, see LSM_ID_XXX
+ * @flags: LSM specific flags
+ * @len: length of the lsm_ctx struct, @ctx and any other data or padding
+ * @ctx_len: the size of @ctx
+ * @ctx: the LSM context value
+ *
+ * The @len field MUST be equal to the size of the lsm_ctx struct
+ * plus any additional padding and/or data placed after @ctx.
+ *
+ * In all cases @ctx_len MUST be equal to the length of @ctx.
+ * If @ctx is a string value it should be nul terminated with
+ * @ctx_len equal to `strlen(@ctx) + 1`. Binary values are
+ * supported.
+ *
+ * The @flags and @ctx fields SHOULD only be interpreted by the
+ * LSM specified by @id; they MUST be set to zero/0 when not used.
+ */
+struct lsm_ctx {
+ __u64 id;
+ __u64 flags;
+ __u64 len;
+ __u64 ctx_len;
+ __u8 ctx[];
+};
+
/*
* ID tokens to identify Linux Security Modules (LSMs)
*
@@ -51,4 +81,10 @@
#define LSM_ATTR_PREV 104
#define LSM_ATTR_SOCKCREATE 105
+/*
+ * LSM_FLAG_XXX definitions identify special handling instructions
+ * for the API.
+ */
+#define LSM_FLAG_SINGLE 0x0001
+
#endif /* _UAPI_LINUX_LSM_H */
@@ -262,6 +262,10 @@ COND_SYSCALL_COMPAT(recvmsg);
/* mm/nommu.c, also with MMU */
COND_SYSCALL(mremap);
+/* security/lsm_syscalls.c */
+COND_SYSCALL(lsm_get_self_attr);
+COND_SYSCALL(lsm_set_self_attr);
+
/* security/keys/keyctl.c */
COND_SYSCALL(add_key);
COND_SYSCALL(request_key);
@@ -7,6 +7,7 @@ obj-$(CONFIG_KEYS) += keys/
# always enable default capabilities
obj-y += commoncap.o
+obj-$(CONFIG_SECURITY) += lsm_syscalls.o
obj-$(CONFIG_MMU) += min_addr.o
# Object file lists
new file mode 100644
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * System calls implementing the Linux Security Module API.
+ *
+ * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com>
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#include <asm/current.h>
+#include <linux/compiler_types.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/security.h>
+#include <linux/stddef.h>
+#include <linux/syscalls.h>
+#include <linux/types.h>
+#include <linux/lsm_hooks.h>
+#include <uapi/linux/lsm.h>
+
+/**
+ * sys_lsm_set_self_attr - Set current task's security module attribute
+ * @attr: which attribute to set
+ * @ctx: the LSM contexts
+ * @size: size of @ctx
+ * @flags: reserved for future use
+ *
+ * Sets the calling task's LSM context. On success this function
+ * returns 0. If the attribute specified cannot be set a negative
+ * value indicating the reason for the error is returned.
+ */
+SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *,
+ ctx, size_t __user, size, u32, flags)
+{
+ return security_setselfattr(attr, ctx, size, flags);
+}
+
+/**
+ * sys_lsm_get_self_attr - Return current task's security module attributes
+ * @attr: which attribute to set
+ * @ctx: the LSM contexts
+ * @size: size of @ctx, updated on return
+ * @flags: reserved for future use
+ *
+ * Returns the calling task's LSM contexts. On success this
+ * function returns the number of @ctx array elements. This value
+ * may be zero if there are no LSM contexts assigned. If @size is
+ * insufficient to contain the return data -E2BIG is returned and
+ * @size is set to the minimum required size. In all other cases
+ * a negative value indicating the error is returned.
+ */
+SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *,
+ ctx, size_t __user *, size, u32, flags)
+{
+ return security_getselfattr(attr, ctx, size, flags);
+}
@@ -2167,6 +2167,116 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode)
}
EXPORT_SYMBOL(security_d_instantiate);
+/**
+ * security_getselfattr - Read an LSM attribute of the current process.
+ * @attr: which attribute to return
+ * @ctx: the user-space destination for the information, or NULL
+ * @size: the size of space available to receive the data
+ * @flags: special handling options. LSM_FLAG_SINGLE indicates that only
+ * attributes associated with the LSM identified in the passed @ctx be
+ * reported
+ *
+ * Returns the number of attributes found on success, negative value
+ * on error. @size is reset to the total size of the data.
+ * If @size is insufficient to contain the data -E2BIG is returned.
+ */
+int security_getselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+ size_t __user *size, u32 __user flags)
+{
+ struct security_hook_list *hp;
+ struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, };
+ u8 __user *base = (u8 __user *)ctx;
+ size_t total = 0;
+ size_t entrysize;
+ size_t left;
+ bool toobig = false;
+ int count = 0;
+ int rc;
+
+ if (attr == 0)
+ return -EINVAL;
+ if (size == NULL)
+ return -EINVAL;
+ if (get_user(left, size))
+ return -EFAULT;
+
+ if ((flags & LSM_FLAG_SINGLE) == LSM_FLAG_SINGLE) {
+ if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
+ return -EFAULT;
+ if (lctx.id == LSM_ID_UNDEF)
+ return -EINVAL;
+ } else if (flags) {
+ return -EINVAL;
+ }
+
+ hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) {
+ if (lctx.id != LSM_ID_UNDEF && lctx.id != hp->lsmid->id)
+ continue;
+ entrysize = left;
+ if (base)
+ ctx = (struct lsm_ctx __user *)(base + total);
+ rc = hp->hook.getselfattr(attr, ctx, &entrysize, flags);
+ if (rc == -EOPNOTSUPP) {
+ rc = 0;
+ continue;
+ }
+ if (rc == -E2BIG) {
+ toobig = true;
+ left = 0;
+ continue;
+ }
+ if (rc < 0)
+ return rc;
+
+ left -= entrysize;
+ total += entrysize;
+ count += rc;
+ }
+ if (put_user(total, size))
+ return -EFAULT;
+ if (toobig)
+ return -E2BIG;
+ if (count == 0)
+ return LSM_RET_DEFAULT(getselfattr);
+ return count;
+}
+
+/**
+ * security_setselfattr - Set an LSM attribute on the current process.
+ * @attr: which attribute to set
+ * @ctx: the user-space source for the information
+ * @size: the size of the data
+ * @flags: reserved for future use, must be 0
+ *
+ * Set an LSM attribute for the current process. The LSM, attribute
+ * and new value are included in @ctx.
+ *
+ * Returns 0 on success, -EINVAL if the input is inconsistent, -EFAULT
+ * if the user buffer is inaccessible or an LSM specific failure.
+ */
+int security_setselfattr(unsigned int __user attr, struct lsm_ctx __user *ctx,
+ size_t __user size, u32 __user flags)
+{
+ struct security_hook_list *hp;
+ struct lsm_ctx lctx;
+
+ if (flags)
+ return -EINVAL;
+ if (size < sizeof(*ctx))
+ return -EINVAL;
+ if (copy_from_user(&lctx, ctx, sizeof(*ctx)))
+ return -EFAULT;
+ if (size < lctx.len || size < lctx.ctx_len + sizeof(ctx) ||
+ lctx.len < lctx.ctx_len + sizeof(ctx))
+ return -EINVAL;
+
+ hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list)
+ if ((hp->lsmid->id) == lctx.id)
+ return hp->hook.setselfattr(attr, ctx, size, flags);
+
+ return LSM_RET_DEFAULT(setselfattr);
+}
+
int security_getprocattr(struct task_struct *p, int lsmid, const char *name,
char **value)
{