diff mbox series

[4/9] ima: Move ima_file_free() into LSM

Message ID 20221013223654.659758-4-keescook@chromium.org
State New
Headers
Series integrity: Move hooks into LSM |

Commit Message

Kees Cook Oct. 13, 2022, 10:36 p.m. UTC 
  The file_free_security hook already exists for managing notification of
released files. Use the LSM hook instead of open-coded stacking.

Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Petr Vorel <pvorel@suse.cz>
Cc: Jonathan McDowell <noodles@fb.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: linux-integrity@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 fs/file_table.c                   | 1 -
 include/linux/ima.h               | 6 ------
 security/integrity/ima/ima_main.c | 3 ++-
 3 files changed, 2 insertions(+), 8 deletions(-)

Comments

Christian Brauner Oct. 18, 2022, 3:02 p.m. UTC | #1 
On Thu, Oct 13, 2022 at 03:36:49PM -0700, Kees Cook wrote:
> The file_free_security hook already exists for managing notification of
> released files. Use the LSM hook instead of open-coded stacking.
> 
> Cc: Mimi Zohar <zohar@linux.ibm.com>
> Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
> Cc: Paul Moore <paul@paul-moore.com>
> Cc: James Morris <jmorris@namei.org>
> Cc: "Serge E. Hallyn" <serge@hallyn.com>
> Cc: Petr Vorel <pvorel@suse.cz>
> Cc: Jonathan McDowell <noodles@fb.com>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Takashi Iwai <tiwai@suse.de>
> Cc: linux-integrity@vger.kernel.org
> Cc: linux-security-module@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  fs/file_table.c                   | 1 -
>  include/linux/ima.h               | 6 ------
>  security/integrity/ima/ima_main.c | 3 ++-
>  3 files changed, 2 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/file_table.c b/fs/file_table.c
> index 99c6796c9f28..fa707d221a43 100644
> --- a/fs/file_table.c
> +++ b/fs/file_table.c
> @@ -311,7 +311,6 @@ static void __fput(struct file *file)
>  	eventpoll_release(file);
>  	locks_remove_file(file);
>  
> -	ima_file_free(file);
>  	if (unlikely(file->f_flags & FASYNC)) {
>  		if (file->f_op->fasync)
>  			file->f_op->fasync(-1, file, 0);
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 6dc5143f89f2..9f18df366064 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -19,7 +19,6 @@ extern enum hash_algo ima_get_current_hash_algo(void);
>  extern int ima_file_check(struct file *file, int mask);
>  extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
>  				    struct inode *inode);
> -extern void ima_file_free(struct file *file);
>  extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
>  				struct dentry *dentry);
>  extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
> @@ -56,11 +55,6 @@ static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
>  {
>  }
>  
> -static inline void ima_file_free(struct file *file)
> -{
> -	return;
> -}
> -
>  static inline void ima_post_path_mknod(struct user_namespace *mnt_userns,
>  				       struct dentry *dentry)
>  {
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index b3b79d030a67..94379ba40b58 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -183,7 +183,7 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint,
>   *
>   * Flag files that changed, based on i_version
>   */
> -void ima_file_free(struct file *file)
> +static void ima_file_free(struct file *file)
>  {
>  	struct inode *inode = file_inode(file);
>  	struct integrity_iint_cache *iint;
> @@ -1085,6 +1085,7 @@ static struct security_hook_list ima_hooks[] __lsm_ro_after_init = {
>  	LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
>  	LSM_HOOK_INIT(mmap_file, ima_file_mmap),
>  	LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
> +	LSM_HOOK_INIT(file_free_security, ima_file_free),

This doesn't work afaict. If the file is opened for writing ima may
update xattrs. But by the time security_file_free() is called
put_file_access() has already been called which will have given up write
access to the file's mount.

So you would have to - just one of the possibilities - have to move
security_file_free() out of file_free() and into the old ima_file_free()
location. But that might cause semantic changes for other LSMs.
Roberto Sassu Oct. 18, 2022, 3:32 p.m. UTC | #2 
On Tue, 2022-10-18 at 17:02 +0200, Christian Brauner wrote:
> On Thu, Oct 13, 2022 at 03:36:49PM -0700, Kees Cook wrote:
> > The file_free_security hook already exists for managing
> > notification of
> > released files. Use the LSM hook instead of open-coded stacking.
> > 
> > Cc: Mimi Zohar <zohar@linux.ibm.com>
> > Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
> > Cc: Paul Moore <paul@paul-moore.com>
> > Cc: James Morris <jmorris@namei.org>
> > Cc: "Serge E. Hallyn" <serge@hallyn.com>
> > Cc: Petr Vorel <pvorel@suse.cz>
> > Cc: Jonathan McDowell <noodles@fb.com>
> > Cc: Borislav Petkov <bp@suse.de>
> > Cc: Takashi Iwai <tiwai@suse.de>
> > Cc: linux-integrity@vger.kernel.org
> > Cc: linux-security-module@vger.kernel.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  fs/file_table.c                   | 1 -
> >  include/linux/ima.h               | 6 ------
> >  security/integrity/ima/ima_main.c | 3 ++-
> >  3 files changed, 2 insertions(+), 8 deletions(-)
> > 
> > diff --git a/fs/file_table.c b/fs/file_table.c
> > index 99c6796c9f28..fa707d221a43 100644
> > --- a/fs/file_table.c
> > +++ b/fs/file_table.c
> > @@ -311,7 +311,6 @@ static void __fput(struct file *file)
> >  	eventpoll_release(file);
> >  	locks_remove_file(file);
> >  
> > -	ima_file_free(file);
> >  	if (unlikely(file->f_flags & FASYNC)) {
> >  		if (file->f_op->fasync)
> >  			file->f_op->fasync(-1, file, 0);
> > diff --git a/include/linux/ima.h b/include/linux/ima.h
> > index 6dc5143f89f2..9f18df366064 100644
> > --- a/include/linux/ima.h
> > +++ b/include/linux/ima.h
> > @@ -19,7 +19,6 @@ extern enum hash_algo
> > ima_get_current_hash_algo(void);
> >  extern int ima_file_check(struct file *file, int mask);
> >  extern void ima_post_create_tmpfile(struct user_namespace
> > *mnt_userns,
> >  				    struct inode *inode);
> > -extern void ima_file_free(struct file *file);
> >  extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
> >  				struct dentry *dentry);
> >  extern int ima_file_hash(struct file *file, char *buf, size_t
> > buf_size);
> > @@ -56,11 +55,6 @@ static inline void
> > ima_post_create_tmpfile(struct user_namespace *mnt_userns,
> >  {
> >  }
> >  
> > -static inline void ima_file_free(struct file *file)
> > -{
> > -	return;
> > -}
> > -
> >  static inline void ima_post_path_mknod(struct user_namespace
> > *mnt_userns,
> >  				       struct dentry *dentry)
> >  {
> > diff --git a/security/integrity/ima/ima_main.c
> > b/security/integrity/ima/ima_main.c
> > index b3b79d030a67..94379ba40b58 100644
> > --- a/security/integrity/ima/ima_main.c
> > +++ b/security/integrity/ima/ima_main.c
> > @@ -183,7 +183,7 @@ static void ima_check_last_writer(struct
> > integrity_iint_cache *iint,
> >   *
> >   * Flag files that changed, based on i_version
> >   */
> > -void ima_file_free(struct file *file)
> > +static void ima_file_free(struct file *file)
> >  {
> >  	struct inode *inode = file_inode(file);
> >  	struct integrity_iint_cache *iint;
> > @@ -1085,6 +1085,7 @@ static struct security_hook_list ima_hooks[]
> > __lsm_ro_after_init = {
> >  	LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
> >  	LSM_HOOK_INIT(mmap_file, ima_file_mmap),
> >  	LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
> > +	LSM_HOOK_INIT(file_free_security, ima_file_free),
> 
> This doesn't work afaict. If the file is opened for writing ima may
> update xattrs. But by the time security_file_free() is called
> put_file_access() has already been called which will have given up
> write
> access to the file's mount.
> 
> So you would have to - just one of the possibilities - have to move
> security_file_free() out of file_free() and into the old
> ima_file_free()
> location. But that might cause semantic changes for other LSMs.

Hi

I also did this work before. In my implementation, I created a new
security hook called security_file_pre_free().

https://github.com/robertosassu/linux/commit/692c9d36fff865435b23b3cb765d31f3584f6263

If useful, the whole patch set is available at:

https://github.com/robertosassu/linux/commits/ima-evm-lsm-v1-devel-v3

Roberto
Kees Cook Oct. 18, 2022, 6:29 p.m. UTC | #3 
On Tue, Oct 18, 2022 at 05:32:40PM +0200, Roberto Sassu wrote:
> I also did this work before. In my implementation, I created a new
> security hook called security_file_pre_free().
> 
> https://github.com/robertosassu/linux/commit/692c9d36fff865435b23b3cb765d31f3584f6263
> 
> If useful, the whole patch set is available at:
> 
> https://github.com/robertosassu/linux/commits/ima-evm-lsm-v1-devel-v3

Ah, lovely! Can you pick this back up and run with it? I mainly did
these a proof-of-concept, but it looks like you got further.
Roberto Sassu Oct. 19, 2022, 6:55 a.m. UTC | #4 
On Tue, 2022-10-18 at 11:29 -0700, Kees Cook wrote:
> On Tue, Oct 18, 2022 at 05:32:40PM +0200, Roberto Sassu wrote:
> > I also did this work before. In my implementation, I created a new
> > security hook called security_file_pre_free().
> > 
> > https://github.com/robertosassu/linux/commit/692c9d36fff865435b23b3cb765d31f3584f6263
> > 
> > If useful, the whole patch set is available at:
> > 
> > https://github.com/robertosassu/linux/commits/ima-evm-lsm-v1-devel-v3
> 
> Ah, lovely! Can you pick this back up and run with it? I mainly did
> these a proof-of-concept, but it looks like you got further.

It was some time ago. If I remember correctly, I got to the point of
running IMA/EVM and passing basic tests.

Will take a look at your patches and comments, and integrate in mines
if something is missing.

Will also send again the prerequisite patch set.

Roberto
Paul Moore Oct. 20, 2022, 3:47 p.m. UTC | #5 
On Wed, Oct 19, 2022 at 2:56 AM Roberto Sassu
<roberto.sassu@huaweicloud.com> wrote:
> On Tue, 2022-10-18 at 11:29 -0700, Kees Cook wrote:
> > On Tue, Oct 18, 2022 at 05:32:40PM +0200, Roberto Sassu wrote:
> > > I also did this work before. In my implementation, I created a new
> > > security hook called security_file_pre_free().
> > >
> > > https://github.com/robertosassu/linux/commit/692c9d36fff865435b23b3cb765d31f3584f6263
> > >
> > > If useful, the whole patch set is available at:
> > >
> > > https://github.com/robertosassu/linux/commits/ima-evm-lsm-v1-devel-v3
> >
> > Ah, lovely! Can you pick this back up and run with it? I mainly did
> > these a proof-of-concept, but it looks like you got further.
>
> It was some time ago. If I remember correctly, I got to the point of
> running IMA/EVM and passing basic tests.
>
> Will take a look at your patches and comments, and integrate in mines
> if something is missing.
>
> Will also send again the prerequisite patch set.

Thanks Roberto, I appreciate you taking the time to resume your
earlier work.  I think this will be a nice improvement and help us
cleanup a lot of code.
diff mbox series

Patch

diff --git a/fs/file_table.c b/fs/file_table.c
index 99c6796c9f28..fa707d221a43 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -311,7 +311,6 @@  static void __fput(struct file *file)
 	eventpoll_release(file);
 	locks_remove_file(file);
 
-	ima_file_free(file);
 	if (unlikely(file->f_flags & FASYNC)) {
 		if (file->f_op->fasync)
 			file->f_op->fasync(-1, file, 0);
diff --git a/include/linux/ima.h b/include/linux/ima.h
index 6dc5143f89f2..9f18df366064 100644
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -19,7 +19,6 @@  extern enum hash_algo ima_get_current_hash_algo(void);
 extern int ima_file_check(struct file *file, int mask);
 extern void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
 				    struct inode *inode);
-extern void ima_file_free(struct file *file);
 extern void ima_post_path_mknod(struct user_namespace *mnt_userns,
 				struct dentry *dentry);
 extern int ima_file_hash(struct file *file, char *buf, size_t buf_size);
@@ -56,11 +55,6 @@  static inline void ima_post_create_tmpfile(struct user_namespace *mnt_userns,
 {
 }
 
-static inline void ima_file_free(struct file *file)
-{
-	return;
-}
-
 static inline void ima_post_path_mknod(struct user_namespace *mnt_userns,
 				       struct dentry *dentry)
 {
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index b3b79d030a67..94379ba40b58 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -183,7 +183,7 @@  static void ima_check_last_writer(struct integrity_iint_cache *iint,
  *
  * Flag files that changed, based on i_version
  */
-void ima_file_free(struct file *file)
+static void ima_file_free(struct file *file)
 {
 	struct inode *inode = file_inode(file);
 	struct integrity_iint_cache *iint;
@@ -1085,6 +1085,7 @@  static struct security_hook_list ima_hooks[] __lsm_ro_after_init = {
 	LSM_HOOK_INIT(bprm_check_security, ima_bprm_check),
 	LSM_HOOK_INIT(mmap_file, ima_file_mmap),
 	LSM_HOOK_INIT(file_mprotect, ima_file_mprotect),
+	LSM_HOOK_INIT(file_free_security, ima_file_free),
 	LSM_HOOK_INIT(kernel_read_file, ima_read_file),
 	LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file),
 	LSM_HOOK_INIT(kernel_load_data, ima_load_data),