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authorMiklos Szeredi <mszeredi@redhat.com>2017-10-30 21:14:56 +0100
committerJan Kara <jack@suse.cz>2017-10-31 17:54:56 +0100
commitf37650f1c7c71cf5180b43229d13b421d81e7170 (patch)
treeff7aab8765170e57aaa8eb117b9c899017b02fe6 /fs/notify/fanotify/fanotify.c
parent9a31d7ad997f55768c687974ce36b759065b49e5 (diff)
downloadlinux-f37650f1c7c71cf5180b43229d13b421d81e7170.tar.bz2
fanotify: fix fsnotify_prepare_user_wait() failure
If fsnotify_prepare_user_wait() fails, we leave the event on the notification list. Which will result in a warning in fsnotify_destroy_event() and later use-after-free. Instead of adding a new helper to remove the event from the list in this case, I opted to move the prepare/finish up into fanotify_handle_event(). This will allow these to be moved further out into the generic code later, and perhaps let us move to non-sleeping RCU. Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Fixes: 05f0e38724e8 ("fanotify: Release SRCU lock when waiting for userspace response") Cc: <stable@vger.kernel.org> # v4.12 Signed-off-by: Jan Kara <jack@suse.cz>
Diffstat (limited to 'fs/notify/fanotify/fanotify.c')
-rw-r--r--fs/notify/fanotify/fanotify.c33
1 files changed, 20 insertions, 13 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 2fa99aeaa095..df3f484e458a 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -64,19 +64,8 @@ static int fanotify_get_response(struct fsnotify_group *group,
pr_debug("%s: group=%p event=%p\n", __func__, group, event);
- /*
- * fsnotify_prepare_user_wait() fails if we race with mark deletion.
- * Just let the operation pass in that case.
- */
- if (!fsnotify_prepare_user_wait(iter_info)) {
- event->response = FAN_ALLOW;
- goto out;
- }
-
wait_event(group->fanotify_data.access_waitq, event->response);
- fsnotify_finish_user_wait(iter_info);
-out:
/* userspace responded, convert to something usable */
switch (event->response) {
case FAN_ALLOW:
@@ -211,9 +200,21 @@ static int fanotify_handle_event(struct fsnotify_group *group,
pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
mask);
+#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
+ if (mask & FAN_ALL_PERM_EVENTS) {
+ /*
+ * fsnotify_prepare_user_wait() fails if we race with mark
+ * deletion. Just let the operation pass in that case.
+ */
+ if (!fsnotify_prepare_user_wait(iter_info))
+ return 0;
+ }
+#endif
+
event = fanotify_alloc_event(inode, mask, data);
+ ret = -ENOMEM;
if (unlikely(!event))
- return -ENOMEM;
+ goto finish;
fsn_event = &event->fse;
ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
@@ -223,7 +224,8 @@ static int fanotify_handle_event(struct fsnotify_group *group,
/* Our event wasn't used in the end. Free it. */
fsnotify_destroy_event(group, fsn_event);
- return 0;
+ ret = 0;
+ goto finish;
}
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
@@ -232,6 +234,11 @@ static int fanotify_handle_event(struct fsnotify_group *group,
iter_info);
fsnotify_destroy_event(group, fsn_event);
}
+finish:
+ if (mask & FAN_ALL_PERM_EVENTS)
+ fsnotify_finish_user_wait(iter_info);
+#else
+finish:
#endif
return ret;
}