From: Chuck Lever <chuck.lever@oracle.com>
Date: Thu, 1 Sep 2022 15:10:05 -0400
Subject: [PATCH] NFSD: Protect against send buffer overflow in NFSv2 READDIR
Git-commit: 00b4492686e0497fdb924a9d4c8f6f99377e176c
Patch-mainline: v6.1
References: bsc#1205128 CVE-2022-43945
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@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: NeilBrown <neilb@suse.com>
---
fs/nfsd/nfsproc.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/fs/nfsd/nfsproc.c
+++ b/fs/nfsd/nfsproc.c
@@ -557,12 +557,11 @@ static void nfsd_init_dirlist_pages(stru
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++;