[PATCH AUTOSEL 5.15 08/11] exec: Distinguish in_execve from in_exec

[PATCH AUTOSEL 5.15 08/11] 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 881390b44cfd..5895f74b252b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1584,6 +1584,7 @@ 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 7bfc2b45cd99..4b88f57130aa 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -902,7 +902,7 @@ 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 753e641f617b..b9f61c26c1d0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1530,6 +1530,7 @@ 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