fanotify: Allow file handle encoding for unhashed events

Allow passing a NULL hash to fanotify_encode_fh and avoid calculating
the hash if not needed.

Link: https://lore.kernel.org/r/20211025192746.66445-15-krisman@collabora.com
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 397ee623ff1e866f03bec750913b6b4825163a45..ec84fee7ad01cc650de7387ff79fd13b8639d7e8 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -403,8 +403,12 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
        fh->type = type;
        fh->len = fh_len;
 
-       /* Mix fh into event merge key */
-       *hash ^= fanotify_hash_fh(fh);
+       /*
+        * Mix fh into event merge key.  Hash might be NULL in case of
+        * unhashed FID events (i.e. FAN_FS_ERROR).
+        */
+       if (hash)
+               *hash ^= fanotify_hash_fh(fh);
 
        return FANOTIFY_FH_HDR_LEN + fh_len;