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

[Sasha Levin]

From: Kees Cook <keescook@xxxxxxxxxxxx>

[ 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@xxxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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