From: Jeff Layton <jlayton@kernel.org> mainline inclusion from mainline-v7.0-rc5 commit 5133b61aaf437e5f25b1b396b14242a6bb0508e2 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/14128 CVE: CVE-2026-31402 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The NFSv4.0 replay cache uses a fixed 112-byte inline buffer (rp_ibuf[NFSD4_REPLAY_ISIZE]) to store encoded operation responses. This size was calculated based on OPEN responses and does not account for LOCK denied responses, which include the conflicting lock owner as a variable-length field up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a LOCK operation is denied due to a conflict with an existing lock that has a large owner, nfsd4_encode_operation() copies the full encoded response into the undersized replay buffer via read_bytes_from_xdr_buf() with no bounds check. This results in a slab-out-of-bounds write of up to 944 bytes past the end of the buffer, corrupting adjacent heap memory. This can be triggered remotely by an unauthenticated attacker with two cooperating NFSv4.0 clients: one sets a lock with a large owner string, then the other requests a conflicting lock to provoke the denial. We could fix this by increasing NFSD4_REPLAY_ISIZE to allow for a full opaque, but that would increase the size of every stateowner, when most lockowners are not that large. Instead, fix this by checking the encoded response length against NFSD4_REPLAY_ISIZE before copying into the replay buffer. If the response is too large, set rp_buflen to 0 to skip caching the replay payload. The status is still cached, and the client already received the correct response on the original request. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@kernel.org Reported-by: Nicholas Carlini <npc@anthropic.com> Tested-by: Nicholas Carlini <npc@anthropic.com> Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Conflicts: fs/nfsd/nfs4xdr.c [Commit 438f81e0e92a ("nfsd: move error choice for incorrect object types to version-specific code.") add mapping for status.] Signed-off-by: Li Lingfeng <lilingfeng3@huawei.com> --- fs/nfsd/nfs4xdr.c | 9 +++++++-- fs/nfsd/state.h | 17 ++++++++++++----- 2 files changed, 19 insertions(+), 7 deletions(-) diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 821c0ad5baa0..b8976c2f17fe 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -5233,9 +5233,14 @@ nfsd4_encode_operation(struct nfsd4_compoundres *resp, struct nfsd4_op *op) int len = xdr->buf->len - post_err_offset; so->so_replay.rp_status = op->status; - so->so_replay.rp_buflen = len; - read_bytes_from_xdr_buf(xdr->buf, post_err_offset, + if (len <= NFSD4_REPLAY_ISIZE) { + so->so_replay.rp_buflen = len; + read_bytes_from_xdr_buf(xdr->buf, + post_err_offset, so->so_replay.rp_buf, len); + } else { + so->so_replay.rp_buflen = 0; + } } status: /* Note that op->status is already in network byte order: */ diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 0e4f98b41364..f398effabeef 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -395,11 +395,18 @@ struct nfs4_client_reclaim { struct xdr_netobj cr_princhash; }; -/* A reasonable value for REPLAY_ISIZE was estimated as follows: - * The OPEN response, typically the largest, requires - * 4(status) + 8(stateid) + 20(changeinfo) + 4(rflags) + 8(verifier) + - * 4(deleg. type) + 8(deleg. stateid) + 4(deleg. recall flag) + - * 20(deleg. space limit) + ~32(deleg. ace) = 112 bytes +/* + * REPLAY_ISIZE is sized for an OPEN response with delegation: + * 4(status) + 8(stateid) + 20(changeinfo) + 4(rflags) + + * 8(verifier) + 4(deleg. type) + 8(deleg. stateid) + + * 4(deleg. recall flag) + 20(deleg. space limit) + + * ~32(deleg. ace) = 112 bytes + * + * Some responses can exceed this. A LOCK denial includes the conflicting + * lock owner, which can be up to 1024 bytes (NFS4_OPAQUE_LIMIT). Responses + * larger than REPLAY_ISIZE are not cached in rp_ibuf; only rp_status is + * saved. Enlarging this constant increases the size of every + * nfs4_stateowner. */ #define NFSD4_REPLAY_ISIZE 112 -- 2.52.0