[PATCH AUTOSEL 6.1 12/15] exec: Distinguish in_execve from in_exec

Sasha Levin
2024-02-02T18:41:20Z

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 283012eb1aeb..541ae913e683 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 0cac69902ec5..4f955709a4ae 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -912,7 +912,7 @@ 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 85617928041c..354c644b6deb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1602,6 +1602,7 @@ 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