5.10-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 640f87c190e0d1b2a0fcb2ecf6d2cd53b1c41991 ]
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 message 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.
Thanks to Aleksi Illikainen and Kari Hulkko for uncovering this issue.
Reported-by: Ben Ronallo Benjamin.Ronallo@synopsys.com Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfsd/nfs3proc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index 1a52f0b06ec32..d808779ab4538 100644 --- a/fs/nfsd/nfs3proc.c +++ b/fs/nfsd/nfs3proc.c @@ -563,13 +563,14 @@ static void nfsd3_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)); + unsigned int sendbuf = min_t(unsigned int, rqstp->rq_res.buflen, + 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), sendbuf); + buf->buflen -= XDR_UNIT * 2; buf->pages = rqstp->rq_next_page; rqstp->rq_next_page += (buf->buflen + PAGE_SIZE - 1) >> PAGE_SHIFT;