Oleg Nesterov e2d8e7bd33 exec: fix the racy usage of fs_struct->in_exec ...

commit af7bb0d2ca upstream.

check_unsafe_exec() sets fs->in_exec under cred_guard_mutex, then execve()
paths clear fs->in_exec lockless. This is fine if exec succeeds, but if it
fails we have the following race:

	T1 sets fs->in_exec = 1, fails, drops cred_guard_mutex

	T2 sets fs->in_exec = 1

	T1 clears fs->in_exec

	T2 continues with fs->in_exec == 0

Change fs/exec.c to clear fs->in_exec with cred_guard_mutex held.

Reported-by: syzbot+1c486d0b62032c82a968@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67dc67f0.050a0220.25ae54.001f.GAE@google.com/
Cc: stable@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250324160003.GA8878@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2025-04-10 14:39:40 +02:00

53 KiB

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