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> --- fs/nfsd/nfsproc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/nfsd/nfsproc.c b/fs/nfsd/nfsproc.c index ddb1902c0a18..4b19cc727ea5 100644 --- a/fs/nfsd/nfsproc.c +++ b/fs/nfsd/nfsproc.c @@ -185,6 +185,7 @@ nfsd_proc_read(struct svc_rqst *rqstp) argp->count, argp->offset); argp->count = min_t(u32, argp->count, NFSSVC_MAXBLKSIZE_V2); + argp->count = min_t(u32, argp->count, rqstp->rq_res.buflen); v = 0; len = argp->count;
