diff options
| author | Jan Kara <jack@suse.cz> | 2019-05-15 16:28:34 +0200 |
|---|---|---|
| committer | Jan Kara <jack@suse.cz> | 2019-05-28 18:10:07 +0200 |
| commit | 0b3b094ac9a7bb1fcf5d694f3ec981e6864a63d3 (patch) | |
| tree | 71e5065d0213798e38d809f0d32fcbba047db6e5 /fs | |
| parent | cd6c84d8f0cdc911df435bb075ba22ce3c605b07 (diff) | |
| download | linux-0b3b094ac9a7bb1fcf5d694f3ec981e6864a63d3.tar.bz2 | |
fanotify: Disallow permission events for proc filesystem
Proc filesystem has special locking rules for various files. Thus
fanotify which opens files on event delivery can easily deadlock
against another process that waits for fanotify permission event to be
handled. Since permission events on /proc have doubtful value anyway,
just disallow them.
Link: https://lore.kernel.org/linux-fsdevel/20190320131642.GE9485@quack2.suse.cz/
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/notify/fanotify/fanotify_user.c | 22 | ||||
| -rw-r--r-- | fs/proc/root.c | 2 |
2 files changed, 23 insertions, 1 deletions
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c index a90bb19dcfa2..91006f47e420 100644 --- a/fs/notify/fanotify/fanotify_user.c +++ b/fs/notify/fanotify/fanotify_user.c @@ -920,6 +920,22 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid) return 0; } +static int fanotify_events_supported(struct path *path, __u64 mask) +{ + /* + * Some filesystems such as 'proc' acquire unusual locks when opening + * files. For them fanotify permission events have high chances of + * deadlocking the system - open done when reporting fanotify event + * blocks on this "unusual" lock while another process holding the lock + * waits for fanotify permission event to be answered. Just disallow + * permission events for such filesystems. + */ + if (mask & FANOTIFY_PERM_EVENTS && + path->mnt->mnt_sb->s_type->fs_flags & FS_DISALLOW_NOTIFY_PERM) + return -EINVAL; + return 0; +} + static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, int dfd, const char __user *pathname) { @@ -1018,6 +1034,12 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask, if (ret) goto fput_and_out; + if (flags & FAN_MARK_ADD) { + ret = fanotify_events_supported(&path, mask); + if (ret) + goto path_put_and_out; + } + if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) { ret = fanotify_test_fid(&path, &__fsid); if (ret) diff --git a/fs/proc/root.c b/fs/proc/root.c index 8b145e7b9661..522199e9525e 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -211,7 +211,7 @@ static struct file_system_type proc_fs_type = { .init_fs_context = proc_init_fs_context, .parameters = &proc_fs_parameters, .kill_sb = proc_kill_sb, - .fs_flags = FS_USERNS_MOUNT, + .fs_flags = FS_USERNS_MOUNT | FS_DISALLOW_NOTIFY_PERM, }; void __init proc_root_init(void) |