| Message ID | 166205941213.1435.18172275008498406790.stgit@manet.1015granger.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fixes for server-side xdr_stream overhaul | expand |
On Thu, 2022-09-01 at 15:10 -0400, Chuck Lever wrote: > 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> > --- > 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 a41cca619338..7a159785499a 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; > > > Reviewed-by: Jeff Layton <jlayton@kernel.org>
diff --git a/fs/nfsd/nfs3proc.c b/fs/nfsd/nfs3proc.c index a41cca619338..7a159785499a 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;
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> --- fs/nfsd/nfs3proc.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)