diff mbox series

[v2,2/5] seccomp, bpf: Introduce SECCOMP_LOAD_FILTER operation

Message ID 20231015232953.84836-3-hengqi.chen@gmail.com
State New
Headers
Series seccomp: Make seccomp filter reusable |

Commit Message

Hengqi Chen Oct. 15, 2023, 11:29 p.m. UTC 
  This patch adds a new operation named SECCOMP_LOAD_FILTER.
It accepts a sock_fprog the same as SECCOMP_SET_MODE_FILTER
but only performs the loading process. If succeed, return a
new fd associated with the JITed BPF program (the filter).
The filter can then be pinned to bpffs using the returned
fd and reused for different processes. To distinguish the
filter from other BPF progs, BPF_PROG_TYPE_SECCOMP is added.

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
---
 include/uapi/linux/bpf.h       |  1 +
 include/uapi/linux/seccomp.h   |  1 +
 kernel/seccomp.c               | 43 ++++++++++++++++++++++++++++++++++
 tools/include/uapi/linux/bpf.h |  1 +
 4 files changed, 46 insertions(+)

Comments

Daniel Borkmann Oct. 16, 2023, 12:44 p.m. UTC | #1 
On 10/16/23 1:29 AM, Hengqi Chen wrote:
> This patch adds a new operation named SECCOMP_LOAD_FILTER.
> It accepts a sock_fprog the same as SECCOMP_SET_MODE_FILTER
> but only performs the loading process. If succeed, return a
> new fd associated with the JITed BPF program (the filter).
> The filter can then be pinned to bpffs using the returned
> fd and reused for different processes. To distinguish the
> filter from other BPF progs, BPF_PROG_TYPE_SECCOMP is added.
> 
> Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> ---
>   include/uapi/linux/bpf.h       |  1 +
>   include/uapi/linux/seccomp.h   |  1 +
>   kernel/seccomp.c               | 43 ++++++++++++++++++++++++++++++++++
>   tools/include/uapi/linux/bpf.h |  1 +
>   4 files changed, 46 insertions(+)
> 
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 7ba61b75bc0e..61c80ffb1724 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -995,6 +995,7 @@ enum bpf_prog_type {
>   	BPF_PROG_TYPE_SK_LOOKUP,
>   	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
>   	BPF_PROG_TYPE_NETFILTER,
> +	BPF_PROG_TYPE_SECCOMP,

Please don't extend UAPI surface if this is not reachable/usable from user
space anyway.

>   enum bpf_attach_type {
> diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
> index dbfc9b37fcae..ee2c83697810 100644
> --- a/include/uapi/linux/seccomp.h
> +++ b/include/uapi/linux/seccomp.h
> @@ -16,6 +16,7 @@
>   #define SECCOMP_SET_MODE_FILTER		1
>   #define SECCOMP_GET_ACTION_AVAIL	2
>   #define SECCOMP_GET_NOTIF_SIZES		3
> +#define SECCOMP_LOAD_FILTER		4
>   
>   /* Valid flags for SECCOMP_SET_MODE_FILTER */
>   #define SECCOMP_FILTER_FLAG_TSYNC		(1UL << 0)
> diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> index faf84fc892eb..c9f6a19f7a4e 100644
> --- a/kernel/seccomp.c
> +++ b/kernel/seccomp.c
> @@ -17,6 +17,7 @@
>   
>   #include <linux/refcount.h>
>   #include <linux/audit.h>
> +#include <linux/bpf.h>
>   #include <linux/compat.h>
>   #include <linux/coredump.h>
>   #include <linux/kmemleak.h>
> @@ -25,6 +26,7 @@
>   #include <linux/sched.h>
>   #include <linux/sched/task_stack.h>
>   #include <linux/seccomp.h>
> +#include <linux/security.h>
>   #include <linux/slab.h>
>   #include <linux/syscalls.h>
>   #include <linux/sysctl.h>
> @@ -2032,12 +2034,48 @@ static long seccomp_set_mode_filter(unsigned int flags,
>   	seccomp_filter_free(prepared);
>   	return ret;
>   }
> +
> +static long seccomp_load_filter(const char __user *filter)
> +{
> +	struct sock_fprog fprog;
> +	struct bpf_prog *prog;
> +	int ret;
> +
> +	ret = seccomp_copy_user_filter(filter, &fprog);
> +	if (ret)
> +		return ret;
> +
> +	ret = seccomp_prepare_prog(&prog, &fprog);
> +	if (ret)
> +		return ret;
> +
> +	ret = security_bpf_prog_alloc(prog->aux);
> +	if (ret) {
> +		bpf_prog_free(prog);
> +		return ret;
> +	}
> +
> +	prog->aux->user = get_current_user();
> +	atomic64_set(&prog->aux->refcnt, 1);
> +	prog->type = BPF_PROG_TYPE_SECCOMP;
> +
> +	ret = bpf_prog_new_fd(prog);
> +	if (ret < 0)
> +		bpf_prog_put(prog);

My bigger concern here is that bpf_prog_new_fd() is only used by eBPF (not cBPF).

Then you get an 'eBPF'-like fd back to user space which you can pass to various
other bpf(2) commands like BPF_OBJ_GET_INFO_BY_FD etc which all have the assumption
that this is a proper looking eBPF prog fd.

There may be breakage/undefined behavior in subtle ways.

I would suggest two potential alternatives :

1) Build a seccomp-specific fd via anon_inode_getfd() so that BPF side does not
    confuse it with bpf_prog_fops and therefore does not recognize it in bpf(2)
    as a prog fd.

2) Extend seccomp where proper eBPF could be supported.

If option 2) is not realistic (where you would get this out of the box), then I
think 1) could be however.

> +	return ret;
> +}
>   #else
>   static inline long seccomp_set_mode_filter(unsigned int flags,
>   					   const char __user *filter)
>   {
>   	return -EINVAL;
>   }
> +
> +static inline long seccomp_load_filter(const char __user *filter)
> +{
> +	return -EINVAL;
> +}
>   #endif
>   
>   static long seccomp_get_action_avail(const char __user *uaction)
> @@ -2099,6 +2137,11 @@ static long do_seccomp(unsigned int op, unsigned int flags,
>   			return -EINVAL;
>   
>   		return seccomp_get_notif_sizes(uargs);
> +	case SECCOMP_LOAD_FILTER:
> +		if (flags != 0)
> +			return -EINVAL;
> +
> +		return seccomp_load_filter(uargs);
>   	default:
>   		return -EINVAL;
>   	}
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 7ba61b75bc0e..61c80ffb1724 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -995,6 +995,7 @@ enum bpf_prog_type {
>   	BPF_PROG_TYPE_SK_LOOKUP,
>   	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
>   	BPF_PROG_TYPE_NETFILTER,
> +	BPF_PROG_TYPE_SECCOMP,
>   };
>   
>   enum bpf_attach_type {
>
kernel test robot Oct. 22, 2023, 11:42 p.m. UTC | #2 
Hi Hengqi,

kernel test robot noticed the following build errors:

[auto build test ERROR on kees/for-next/seccomp]
[also build test ERROR on bpf-next/master bpf/master linus/master v6.6-rc6 next-20231020]
[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/Hengqi-Chen/seccomp-Refactor-filter-copy-create-for-reuse/20231017-134654
base:   https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/seccomp
patch link:    https://lore.kernel.org/r/20231015232953.84836-3-hengqi.chen%40gmail.com
patch subject: [PATCH v2 2/5] seccomp, bpf: Introduce SECCOMP_LOAD_FILTER operation
config: sh-shx3_defconfig (https://download.01.org/0day-ci/archive/20231023/202310230704.Uif0R7cz-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231023/202310230704.Uif0R7cz-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310230704.Uif0R7cz-lkp@intel.com/

All errors (new ones prefixed by >>):

   kernel/seccomp.c: In function 'seccomp_load_filter':
>> kernel/seccomp.c:2052:15: error: implicit declaration of function 'security_bpf_prog_alloc'; did you mean 'security_msg_msg_alloc'? [-Werror=implicit-function-declaration]
    2052 |         ret = security_bpf_prog_alloc(prog->aux);
         |               ^~~~~~~~~~~~~~~~~~~~~~~
         |               security_msg_msg_alloc
>> kernel/seccomp.c:2062:15: error: implicit declaration of function 'bpf_prog_new_fd'; did you mean 'bpf_prog_get_ok'? [-Werror=implicit-function-declaration]
    2062 |         ret = bpf_prog_new_fd(prog);
         |               ^~~~~~~~~~~~~~~
         |               bpf_prog_get_ok
   cc1: some warnings being treated as errors


vim +2052 kernel/seccomp.c

  2037	
  2038	static long seccomp_load_filter(const char __user *filter)
  2039	{
  2040		struct sock_fprog fprog;
  2041		struct bpf_prog *prog;
  2042		int ret;
  2043	
  2044		ret = seccomp_copy_user_filter(filter, &fprog);
  2045		if (ret)
  2046			return ret;
  2047	
  2048		ret = seccomp_prepare_prog(&prog, &fprog);
  2049		if (ret)
  2050			return ret;
  2051	
> 2052		ret = security_bpf_prog_alloc(prog->aux);
  2053		if (ret) {
  2054			bpf_prog_free(prog);
  2055			return ret;
  2056		}
  2057	
  2058		prog->aux->user = get_current_user();
  2059		atomic64_set(&prog->aux->refcnt, 1);
  2060		prog->type = BPF_PROG_TYPE_SECCOMP;
  2061	
> 2062		ret = bpf_prog_new_fd(prog);
  2063		if (ret < 0)
  2064			bpf_prog_put(prog);
  2065	
  2066		return ret;
  2067	}
  2068	#else
  2069	static inline long seccomp_set_mode_filter(unsigned int flags,
  2070						   const char __user *filter)
  2071	{
  2072		return -EINVAL;
  2073	}
  2074
Hengqi Chen Oct. 23, 2023, 4:17 a.m. UTC | #3 
On Mon, Oct 16, 2023 at 8:44 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 10/16/23 1:29 AM, Hengqi Chen wrote:
> > This patch adds a new operation named SECCOMP_LOAD_FILTER.
> > It accepts a sock_fprog the same as SECCOMP_SET_MODE_FILTER
> > but only performs the loading process. If succeed, return a
> > new fd associated with the JITed BPF program (the filter).
> > The filter can then be pinned to bpffs using the returned
> > fd and reused for different processes. To distinguish the
> > filter from other BPF progs, BPF_PROG_TYPE_SECCOMP is added.
> >
> > Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
> > ---
> >   include/uapi/linux/bpf.h       |  1 +
> >   include/uapi/linux/seccomp.h   |  1 +
> >   kernel/seccomp.c               | 43 ++++++++++++++++++++++++++++++++++
> >   tools/include/uapi/linux/bpf.h |  1 +
> >   4 files changed, 46 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index 7ba61b75bc0e..61c80ffb1724 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -995,6 +995,7 @@ enum bpf_prog_type {
> >       BPF_PROG_TYPE_SK_LOOKUP,
> >       BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> >       BPF_PROG_TYPE_NETFILTER,
> > +     BPF_PROG_TYPE_SECCOMP,
>
> Please don't extend UAPI surface if this is not reachable/usable from user
> space anyway.
>
> >   enum bpf_attach_type {
> > diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
> > index dbfc9b37fcae..ee2c83697810 100644
> > --- a/include/uapi/linux/seccomp.h
> > +++ b/include/uapi/linux/seccomp.h
> > @@ -16,6 +16,7 @@
> >   #define SECCOMP_SET_MODE_FILTER             1
> >   #define SECCOMP_GET_ACTION_AVAIL    2
> >   #define SECCOMP_GET_NOTIF_SIZES             3
> > +#define SECCOMP_LOAD_FILTER          4
> >
> >   /* Valid flags for SECCOMP_SET_MODE_FILTER */
> >   #define SECCOMP_FILTER_FLAG_TSYNC           (1UL << 0)
> > diff --git a/kernel/seccomp.c b/kernel/seccomp.c
> > index faf84fc892eb..c9f6a19f7a4e 100644
> > --- a/kernel/seccomp.c
> > +++ b/kernel/seccomp.c
> > @@ -17,6 +17,7 @@
> >
> >   #include <linux/refcount.h>
> >   #include <linux/audit.h>
> > +#include <linux/bpf.h>
> >   #include <linux/compat.h>
> >   #include <linux/coredump.h>
> >   #include <linux/kmemleak.h>
> > @@ -25,6 +26,7 @@
> >   #include <linux/sched.h>
> >   #include <linux/sched/task_stack.h>
> >   #include <linux/seccomp.h>
> > +#include <linux/security.h>
> >   #include <linux/slab.h>
> >   #include <linux/syscalls.h>
> >   #include <linux/sysctl.h>
> > @@ -2032,12 +2034,48 @@ static long seccomp_set_mode_filter(unsigned int flags,
> >       seccomp_filter_free(prepared);
> >       return ret;
> >   }
> > +
> > +static long seccomp_load_filter(const char __user *filter)
> > +{
> > +     struct sock_fprog fprog;
> > +     struct bpf_prog *prog;
> > +     int ret;
> > +
> > +     ret = seccomp_copy_user_filter(filter, &fprog);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = seccomp_prepare_prog(&prog, &fprog);
> > +     if (ret)
> > +             return ret;
> > +
> > +     ret = security_bpf_prog_alloc(prog->aux);
> > +     if (ret) {
> > +             bpf_prog_free(prog);
> > +             return ret;
> > +     }
> > +
> > +     prog->aux->user = get_current_user();
> > +     atomic64_set(&prog->aux->refcnt, 1);
> > +     prog->type = BPF_PROG_TYPE_SECCOMP;
> > +
> > +     ret = bpf_prog_new_fd(prog);
> > +     if (ret < 0)
> > +             bpf_prog_put(prog);
>
> My bigger concern here is that bpf_prog_new_fd() is only used by eBPF (not cBPF).
>
> Then you get an 'eBPF'-like fd back to user space which you can pass to various
> other bpf(2) commands like BPF_OBJ_GET_INFO_BY_FD etc which all have the assumption
> that this is a proper looking eBPF prog fd.
>
> There may be breakage/undefined behavior in subtle ways.
>
> I would suggest two potential alternatives :
>
> 1) Build a seccomp-specific fd via anon_inode_getfd() so that BPF side does not
>     confuse it with bpf_prog_fops and therefore does not recognize it in bpf(2)
>     as a prog fd.
>
> 2) Extend seccomp where proper eBPF could be supported.
>
> If option 2) is not realistic (where you would get this out of the box), then I
> think 1) could be however.
>

The intention is to use bpffs, so we need a bpf prog fd.
I prefer option 2, though it requires a bit of work.
That way, we could also write seccomp filter in eBPF language.

Kees, could you share your opinions ? If you have no objection,
I will continue this work.

> > +     return ret;
> > +}
> >   #else
> >   static inline long seccomp_set_mode_filter(unsigned int flags,
> >                                          const char __user *filter)
> >   {
> >       return -EINVAL;
> >   }
> > +
> > +static inline long seccomp_load_filter(const char __user *filter)
> > +{
> > +     return -EINVAL;
> > +}
> >   #endif
> >
> >   static long seccomp_get_action_avail(const char __user *uaction)
> > @@ -2099,6 +2137,11 @@ static long do_seccomp(unsigned int op, unsigned int flags,
> >                       return -EINVAL;
> >
> >               return seccomp_get_notif_sizes(uargs);
> > +     case SECCOMP_LOAD_FILTER:
> > +             if (flags != 0)
> > +                     return -EINVAL;
> > +
> > +             return seccomp_load_filter(uargs);
> >       default:
> >               return -EINVAL;
> >       }
> > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> > index 7ba61b75bc0e..61c80ffb1724 100644
> > --- a/tools/include/uapi/linux/bpf.h
> > +++ b/tools/include/uapi/linux/bpf.h
> > @@ -995,6 +995,7 @@ enum bpf_prog_type {
> >       BPF_PROG_TYPE_SK_LOOKUP,
> >       BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
> >       BPF_PROG_TYPE_NETFILTER,
> > +     BPF_PROG_TYPE_SECCOMP,
> >   };
> >
> >   enum bpf_attach_type {
> >
>
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7ba61b75bc0e..61c80ffb1724 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -995,6 +995,7 @@  enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
 	BPF_PROG_TYPE_NETFILTER,
+	BPF_PROG_TYPE_SECCOMP,
 };
 
 enum bpf_attach_type {
diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h
index dbfc9b37fcae..ee2c83697810 100644
--- a/include/uapi/linux/seccomp.h
+++ b/include/uapi/linux/seccomp.h
@@ -16,6 +16,7 @@ 
 #define SECCOMP_SET_MODE_FILTER		1
 #define SECCOMP_GET_ACTION_AVAIL	2
 #define SECCOMP_GET_NOTIF_SIZES		3
+#define SECCOMP_LOAD_FILTER		4
 
 /* Valid flags for SECCOMP_SET_MODE_FILTER */
 #define SECCOMP_FILTER_FLAG_TSYNC		(1UL << 0)
diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index faf84fc892eb..c9f6a19f7a4e 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -17,6 +17,7 @@ 
 
 #include <linux/refcount.h>
 #include <linux/audit.h>
+#include <linux/bpf.h>
 #include <linux/compat.h>
 #include <linux/coredump.h>
 #include <linux/kmemleak.h>
@@ -25,6 +26,7 @@ 
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/seccomp.h>
+#include <linux/security.h>
 #include <linux/slab.h>
 #include <linux/syscalls.h>
 #include <linux/sysctl.h>
@@ -2032,12 +2034,48 @@  static long seccomp_set_mode_filter(unsigned int flags,
 	seccomp_filter_free(prepared);
 	return ret;
 }
+
+static long seccomp_load_filter(const char __user *filter)
+{
+	struct sock_fprog fprog;
+	struct bpf_prog *prog;
+	int ret;
+
+	ret = seccomp_copy_user_filter(filter, &fprog);
+	if (ret)
+		return ret;
+
+	ret = seccomp_prepare_prog(&prog, &fprog);
+	if (ret)
+		return ret;
+
+	ret = security_bpf_prog_alloc(prog->aux);
+	if (ret) {
+		bpf_prog_free(prog);
+		return ret;
+	}
+
+	prog->aux->user = get_current_user();
+	atomic64_set(&prog->aux->refcnt, 1);
+	prog->type = BPF_PROG_TYPE_SECCOMP;
+
+	ret = bpf_prog_new_fd(prog);
+	if (ret < 0)
+		bpf_prog_put(prog);
+
+	return ret;
+}
 #else
 static inline long seccomp_set_mode_filter(unsigned int flags,
 					   const char __user *filter)
 {
 	return -EINVAL;
 }
+
+static inline long seccomp_load_filter(const char __user *filter)
+{
+	return -EINVAL;
+}
 #endif
 
 static long seccomp_get_action_avail(const char __user *uaction)
@@ -2099,6 +2137,11 @@  static long do_seccomp(unsigned int op, unsigned int flags,
 			return -EINVAL;
 
 		return seccomp_get_notif_sizes(uargs);
+	case SECCOMP_LOAD_FILTER:
+		if (flags != 0)
+			return -EINVAL;
+
+		return seccomp_load_filter(uargs);
 	default:
 		return -EINVAL;
 	}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7ba61b75bc0e..61c80ffb1724 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -995,6 +995,7 @@  enum bpf_prog_type {
 	BPF_PROG_TYPE_SK_LOOKUP,
 	BPF_PROG_TYPE_SYSCALL, /* a program that can execute syscalls */
 	BPF_PROG_TYPE_NETFILTER,
+	BPF_PROG_TYPE_SECCOMP,
 };
 
 enum bpf_attach_type {