On Thu, 2022-09-01 at 15:10 -0400, Chuck Lever wrote:
> Restore the previous limit on the @count argument to prevent a
> buffer overflow attack.
>
> Fixes: 53b1119a6e50 ("NFSD: Fix READDIR buffer overflow")
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfsd/nfsproc.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c
> index 7381972f1677..ddb1902c0a18 100644
> --- a/fs/nfsd/nfsproc.c
> +++ b/fs/nfsd/nfsproc.c
> @@ -567,12 +567,11 @@ static void nfsd_init_dirlist_pages(struct svc_rqst *rqstp,
> struct xdr_buf *buf = &resp->dirlist;
> struct xdr_stream *xdr = &resp->xdr;
>
> - count = clamp(count, (u32)(XDR_UNIT * 2), svc_max_payload(rqstp));
> -
> memset(buf, 0, sizeof(*buf));
>
> /* Reserve room for the NULL ptr & eof flag (-2 words) */
> - buf->buflen = count - XDR_UNIT * 2;
> + buf->buflen = clamp(count, (u32)(XDR_UNIT * 2), (u32)PAGE_SIZE);
> + buf->buflen -= XDR_UNIT * 2;
> buf->pages = rqstp->rq_next_page;
> rqstp->rq_next_page++;
>
>
>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
