[BUG][PATCH][2.6.36-rc3] fanotify: Do not ignore result of permission decisions

[Tvrtko Ursulin]

Current code ignores access replies to permission decisions so
fix it in a way which will allow all listeners to still receive
non permission events.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
---
 fs/notify/fsnotify.c             |   25 +++++++++++++++++--------
 include/linux/fsnotify_backend.h |    4 ++++
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 3680242..37fd072 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -224,7 +224,7 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
        struct fsnotify_group *inode_group, *vfsmount_group;
        struct fsnotify_event *event = NULL;
        struct vfsmount *mnt;
-       int idx, ret = 0;
+       int idx, ret = 0, res;
        /* global tests shouldn't care about events on child only the specific event */
        __u32 test_mask = (mask & ~FS_EVENT_ON_CHILD);

@@ -275,18 +275,27 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,

                if (inode_group > vfsmount_group) {
                        /* handle inode */
-                       send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
-                                     data_is, cookie, file_name, &event);
+                       res = send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
+                                           data_is, cookie, file_name, &event);
                        /* we didn't use the vfsmount_mark */
                        vfsmount_group = NULL;
                } else if (vfsmount_group > inode_group) {
-                       send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
-                                     data_is, cookie, file_name, &event);
+                       res = send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
+                                           data_is, cookie, file_name, &event);
                        inode_group = NULL;
                } else {
-                       send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
-                                     mask, data, data_is, cookie, file_name,
-                                     &event);
+                       res = send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
+                                           mask, data, data_is, cookie, file_name,
+                                           &event);
+               }
+
+               /* If a listener denied on a permission hook we will remember the reason
+                  and run the rest with a non-permission mask only. This allows other
+                  listeners to receive non-permission notifications but we do not care
+                  about further permission checks. */
+               if (unlikely((res == -EPERM) && (mask & FS_ALL_PERM_EVENTS))) {
+                       mask &= ~FS_ALL_PERM_EVENTS;
+                       ret = res;
                }

                if (inode_group)
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index e40190d..c8aea03 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -64,6 +64,10 @@

 #define FS_MOVE                        (FS_MOVED_FROM | FS_MOVED_TO)

+/* All events which require a permission response from userspace */
+#define FS_ALL_PERM_EVENTS (FS_OPEN_PERM |\
+                           FS_ACCESS_PERM)
+
 #define ALL_FSNOTIFY_EVENTS (FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
                             FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | FS_OPEN | \
                             FS_MOVED_FROM | FS_MOVED_TO | FS_CREATE | \

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