Patch "fanotify: WARN_ON against too large file handles" has been added to the 5.10-stable tree

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This is a note to let you know that I've just added the patch titled

    fanotify: WARN_ON against too large file handles

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fanotify-warn_on-against-too-large-file-handles.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 125e8a5a7b76b37d8bfd92185238fc6d8ca67256
Author: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
Date:   Mon Oct 25 16:27:40 2021 -0300

    fanotify: WARN_ON against too large file handles
    
    [ Upstream commit 572c28f27a269f88e2d8d7b6b1507f114d637337 ]
    
    struct fanotify_error_event, at least, is preallocated and isn't able to
    to handle arbitrarily large file handles.  Future-proof the code by
    complaining loudly if a handle larger than MAX_HANDLE_SZ is ever found.
    
    Link: https://lore.kernel.org/r/20211025192746.66445-26-krisman@xxxxxxxxxxxxx
    Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>
    Reviewed-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Gabriel Krisman Bertazi <krisman@xxxxxxxxxxxxx>
    Signed-off-by: Jan Kara <jack@xxxxxxx>
    Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index cedcb15468043..45df610debbe4 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -360,13 +360,23 @@ static u32 fanotify_group_event_mask(struct fsnotify_group *group,
 static int fanotify_encode_fh_len(struct inode *inode)
 {
 	int dwords = 0;
+	int fh_len;
 
 	if (!inode)
 		return 0;
 
 	exportfs_encode_inode_fh(inode, NULL, &dwords, NULL);
+	fh_len = dwords << 2;
 
-	return dwords << 2;
+	/*
+	 * struct fanotify_error_event might be preallocated and is
+	 * limited to MAX_HANDLE_SZ.  This should never happen, but
+	 * safeguard by forcing an invalid file handle.
+	 */
+	if (WARN_ON_ONCE(fh_len > MAX_HANDLE_SZ))
+		return 0;
+
+	return fh_len;
 }
 
 /*




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