Re: [PATCH] virtiofs: validate fixed-output response length

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Sun, Oct 04, 2026 at 09:34:05PM +0900, sungbyeongchan wrote:
> A short successful virtiofs response can leave the fixed-output
> portion of the request argument buffer unwritten. The completion path
> nevertheless copies the full declared output to the request destination,
> allowing stale allocator contents to reach callers such as
> fuse_statfs().
> 
> Require successful fixed-output responses to contain their complete
> declared output. Continue to permit a shorter final argument only for
> out_argvar requests, and do not copy output arguments from error
> replies.
> 
> A header-only FUSE_STATFS success returned stale fields in nine of
> nine calls across three boots. The patched kernel rejected the short
> response in three boots and preserved complete replies and existing
> error controls.
> 
> Fixes: a62a8ef9d97d ("virtio-fs: add virtiofs filesystem")
> Signed-off-by: sungbyeongchan <tjdqudcks0424@naver.com>
> ---
>  fs/fuse/virtio_fs.c | 26 ++++++++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

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