From eea1fbb9b4e49715105738504ba545af4c5a6349 Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Wed, 13 Jul 2016 01:37:22 +0100 Subject: [PATCH] fanotify: Taint on use of FANOTIFY_ACCESS_PERMISSIONS Various free and proprietary AV products use this feature and users apparently want it. But punting access checks to userland seems like an easy way to deadlock the system, and there will be nothing we can do about that. So warn and taint the kernel if this feature is actually used. Gbp-Pq: Topic debian Gbp-Pq: Name fanotify-taint-on-use-of-fanotify_access_permissions.patch --- fs/notify/fanotify/fanotify_user.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index 4b3437d70e7..cea26c0c751 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -869,6 +869,14 @@ SYSCALL_DEFINE5(fanotify_mark, int, fanotify_fd, unsigned int, flags, #endif return -EINVAL; +#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS + if (mask & FAN_ALL_PERM_EVENTS) { + pr_warn_once("%s (%d): Using fanotify permission checks may lead to deadlock; tainting kernel\n", + current->comm, current->pid); + add_taint(TAINT_USER, LOCKDEP_STILL_OK); + } +#endif + f = fdget(fanotify_fd); if (unlikely(!f.file)) return -EBADF; -- 2.30.2