This is a note to let you know that I've just added the patch titled
NFSD: Protect against send buffer overflow in NFSv3 READ
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:
nfsd-protect-against-send-buffer-overflow-in-nfsv3-r.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 70c8857d58aed91598f46eab9e8541671ec22e86
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Thu Sep 1 15:10:24 2022 -0400
NFSD: Protect against send buffer overflow in NFSv3 READ
[ Upstream commit fa6be9cc6e80ec79892ddf08a8c10cabab9baf38 ]
Since before the git era, NFSD has conserved the number of pages
held by each nfsd thread by combining the RPC receive and send
buffers into a single array of pages. This works because there are
no cases where an operation needs a large RPC Call message and a
large RPC Reply at the same time.
Once an RPC Call has been received, svc_process() updates
svc_rqst::rq_res to describe the part of rq_pages that can be
used for constructing the Reply. This means that the send buffer
(rq_res) shrinks when the received RPC record containing the RPC
Call is large.
A client can force this shrinkage on TCP by sending a correctly-
formed RPC Call header contained in an RPC record that is
excessively large. The full maximum payload size cannot be
constructed in that case.
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c
index d808779ab4538..8679c41746027 100644
--- a/fs/nfsd/nfs3proc.c
+++ b/fs/nfsd/nfs3proc.c
@@ -150,7 +150,6 @@ nfsd3_proc_read(struct svc_rqst *rqstp)
{
struct nfsd3_readargs *argp = rqstp->rq_argp;
struct nfsd3_readres *resp = rqstp->rq_resp;
- u32 max_blocksize = svc_max_payload(rqstp);
unsigned int len;
int v;
@@ -159,7 +158,8 @@ nfsd3_proc_read(struct svc_rqst *rqstp)
(unsigned long) argp->count,
(unsigned long long) argp->offset);
- argp->count = min_t(u32, argp->count, max_blocksize);
+ argp->count = min_t(u32, argp->count, svc_max_payload(rqstp));
+ argp->count = min_t(u32, argp->count, rqstp->rq_res.buflen);
if (argp->offset > (u64)OFFSET_MAX)
argp->offset = (u64)OFFSET_MAX;
if (argp->offset + argp->count > (u64)OFFSET_MAX)
