fanotify: Encode empty file handle when no inode is provided

Instead of failing, encode an invalid file handle in fanotify_encode_fh
if no inode is provided.  This bogus file handle will be reported by
FAN_FS_ERROR for non-inode errors.

Link: https://lore.kernel.org/r/20211025192746.66445-16-krisman@collabora.com
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
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 ec84fee..c64d61b 100644 (file)
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -370,8 +370,14 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
        fh->type = FILEID_ROOT;
        fh->len = 0;
        fh->flags = 0;
+
+       /*
+        * Invalid FHs are used by FAN_FS_ERROR for errors not
+        * linked to any inode. The f_handle won't be reported
+        * back to userspace.
+        */
        if (!inode)
-               return 0;
+               goto out;
 
        /*
         * !gpf means preallocated variable size fh, but fh_len could
@@ -403,6 +409,7 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
        fh->type = type;
        fh->len = fh_len;
 
+out:
        /*
         * Mix fh into event merge key.  Hash might be NULL in case of
         * unhashed FID events (i.e. FAN_FS_ERROR).