6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever [ Upstream commit af6f0e06bed818ee7fc8b869915964410020a1c5 ] The RPC/RDMA Read list decoder stores wire-supplied segment lengths without validation. xdr_count_read_segments() checks 4-byte alignment for non-zero position values but does not cap the segment length. An oversized rs_length reaches svc_rdma_build_read_segment(), which derives nr_bvec from it and can drive a large dynamic bvec allocation before verifying that enough rq_pages remain. If the post-allocation page-overrun guard fires, the freshly acquired rw context is not returned, leaking the resource. Reject any segment whose length exceeds the receive context's page budget during Read list decoding, consistent with how xdr_check_write_chunk() bounds Write segment counts against rc_maxpages. Also return the rw context on the existing post-allocation overrun path in svc_rdma_build_read_segment(), keeping that defensive guard balanced. Fixes: 5ee62b4a9113 ("svcrdma: use bvec-based RDMA read/write API") Cc: stable@vger.kernel.org Acked-by: Jeff Layton Link: https://patch.msgid.link/20260526-rpc-kernel-bugs-v1-3-e251306ccca9@oracle.com Signed-off-by: Chuck Lever Stable-dep-of: 0ca487abb3bd ("svcrdma: Reject Read lists that exceed the page budget") Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 2 ++ net/sunrpc/xprtrdma/svc_rdma_rw.c | 5 +++-- 2 files changed, 5 insertions(+), 2 deletions(-) --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -448,6 +448,8 @@ static bool xdr_count_read_segments(stru xdr_decode_read_segment(p, &position, &handle, &length, &offset); + if (length > rctxt->rc_maxpages << PAGE_SHIFT) + return false; if (position) { if (position & 3) return false; --- a/net/sunrpc/xprtrdma/svc_rdma_rw.c +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c @@ -766,7 +766,7 @@ static int svc_rdma_build_read_segment(s len -= seg_len; if (len && ((head->rc_curpage + 1) > rqstp->rq_maxpages)) - goto out_overrun; + goto out_put; } ret = svc_rdma_rw_ctx_init(rdma, ctxt, segment->rs_offset, @@ -779,7 +779,8 @@ static int svc_rdma_build_read_segment(s cc->cc_sqecount += ret; return 0; -out_overrun: +out_put: + svc_rdma_put_rw_ctxt(rdma, ctxt); trace_svcrdma_page_overrun_err(&cc->cc_cid, head->rc_curpage); return -EINVAL; }