[PATCH AUTOSEL 5.10 7/8] exec: Distinguish in_execve from in_exec

[PATCH AUTOSEL 5.10 7/8] exec: Distinguish in_execve from in_exec

[Sasha Levin]

From: Kees Cook <keescook@chromium.org>

[ Upstream commit 90383cc07895183c75a0db2460301c2ffd912359 ]

Just to help distinguish the fs->in_exec flag from the current->in_execve
flag, add comments in check_unsafe_exec() and copy_fs() for more
context. Also note that in_execve is only used by TOMOYO now.

Cc: Kentaro Takeda <takedakn@nttdata.co.jp>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/exec.c             | 1 +
 include/linux/sched.h | 2 +-
 kernel/fork.c         | 1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/exec.c b/fs/exec.c
index 983295c0b8ac..b809f4a39296 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1565,6 +1565,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
 	}
 	rcu_read_unlock();
 
+	/* "users" and "in_exec" locked for copy_fs() */
 	if (p->fs->users > n_fs)
 		bprm->unsafe |= LSM_UNSAFE_SHARE;
 	else
diff --git a/include/linux/sched.h b/include/linux/sched.h
index aa015416c569..65cfe85de8d5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -806,7 +806,7 @@ struct task_struct {
 	 */
 	unsigned			sched_remote_wakeup:1;
 
-	/* Bit to tell LSMs we're in execve(): */
+	/* Bit to tell TOMOYO we're in execve(): */
 	unsigned			in_execve:1;
 	unsigned			in_iowait:1;
 #ifndef TIF_RESTORE_SIGMASK
diff --git a/kernel/fork.c b/kernel/fork.c
index 633b0af1d1a7..906dbaf25058 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1452,6 +1452,7 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
 	if (clone_flags & CLONE_FS) {
 		/* tsk->fs is already what we want */
 		spin_lock(&fs->lock);
+		/* "users" and "in_exec" locked for check_unsafe_exec() */
 		if (fs->in_exec) {
 			spin_unlock(&fs->lock);
 			return -EAGAIN;
-- 
2.43.0

Re: [PATCH AUTOSEL 5.10 7/8] exec: Distinguish in_execve from in_exec

[Pavel Machek]

[-- Attachment #1: Type: text/plain, Size: 1783 bytes --]

Hi!

> From: Kees Cook <keescook@chromium.org>
> 
> [ Upstream commit 90383cc07895183c75a0db2460301c2ffd912359 ]
> 
> Just to help distinguish the fs->in_exec flag from the current->in_execve
> flag, add comments in check_unsafe_exec() and copy_fs() for more
> context. Also note that in_execve is only used by TOMOYO now.

These are just a whitespace changes, we should not need them.

Best regards,
								Pavel

> +++ b/fs/exec.c
> @@ -1565,6 +1565,7 @@ static void check_unsafe_exec(struct linux_binprm *bprm)
>  	}
>  	rcu_read_unlock();
>  
> +	/* "users" and "in_exec" locked for copy_fs() */
>  	if (p->fs->users > n_fs)
>  		bprm->unsafe |= LSM_UNSAFE_SHARE;
>  	else
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index aa015416c569..65cfe85de8d5 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -806,7 +806,7 @@ struct task_struct {
>  	 */
>  	unsigned			sched_remote_wakeup:1;
>  
> -	/* Bit to tell LSMs we're in execve(): */
> +	/* Bit to tell TOMOYO we're in execve(): */
>  	unsigned			in_execve:1;
>  	unsigned			in_iowait:1;
>  #ifndef TIF_RESTORE_SIGMASK
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 633b0af1d1a7..906dbaf25058 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -1452,6 +1452,7 @@ static int copy_fs(unsigned long clone_flags, struct task_struct *tsk)
>  	if (clone_flags & CLONE_FS) {
>  		/* tsk->fs is already what we want */
>  		spin_lock(&fs->lock);
> +		/* "users" and "in_exec" locked for check_unsafe_exec() */
>  		if (fs->in_exec) {
>  			spin_unlock(&fs->lock);
>  			return -EAGAIN;

-- 
DENX Software Engineering GmbH,        Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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Re: [PATCH AUTOSEL 5.10 7/8] exec: Distinguish in_execve from in_exec

[Sasha Levin]

On Sun, Feb 18, 2024 at 08:12:56PM +0100, Pavel Machek wrote:
>Hi!
>
>> From: Kees Cook <keescook@chromium.org>
>>
>> [ Upstream commit 90383cc07895183c75a0db2460301c2ffd912359 ]
>>
>> Just to help distinguish the fs->in_exec flag from the current->in_execve
>> flag, add comments in check_unsafe_exec() and copy_fs() for more
>> context. Also note that in_execve is only used by TOMOYO now.
>
>These are just a whitespace changes, we should not need them.

Dropped, thanks!

-- 
Thanks,
Sasha