From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB1AB32ED34 for ; Fri, 20 Mar 2026 11:39:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774006784; cv=none; b=TsTIM4Qi+NM5cb7Seoo+17HlGtO71Zp1El4F18zo+L8Rcq2L4XWHsVa2E6qvWX9mmRJZbkKvXUzXyAjsOrOtrlgFo+yIMpC2gpiI/ZUtY1nvwm5YUFiG37t8Y3SGxQWf6GSfLpxxa7lhmCPrWlZpH51OpwE0v9K0K88ED0yL7EE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774006784; c=relaxed/simple; bh=ZwTsAoDc5qO2yX6984ElcNpjyNpsuXnZ1BK3DEOf3gc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=aC1NlCJ6efYBAEzt15cX2ekZ+a96ftZpCMjJEYSP7lBc+5sb35znVqm+Vrw/eFm/WK3zri5CSolMRVYEyJyb7fykaybs0IXKwHaK2zxUaQF9N05DNjSZ3kCRLPEBX9Tgv2xIRzYm+v6VJcjnq16DlmZO9rmmyWghlBoMR2T/UNg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YiZc9rgZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YiZc9rgZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8505C4CEF7; Fri, 20 Mar 2026 11:39:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774006784; bh=ZwTsAoDc5qO2yX6984ElcNpjyNpsuXnZ1BK3DEOf3gc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YiZc9rgZ+VUYbEcRxxJ3KRVwi7JHuPsNQ8pS7Ad8h94M1H5m/C3FzGkTCwK9c5xU1 Nwwy84Jg5wcr5DOjSdD4fTpBnOU6wMgF4UQ862cePCS/X1kEdkpZakylPPv7sTLUku cv1tqa2h3KFSNzsKZMAiHwhSX4n5UOaZQw1WxK6bQd61FiEIQhdTAf5db3Tp0hYVkg fabspnCgY7vtdcLnl1h8vZNjTQw6a7m9j++ZLuKObIIfpnxSqAiW7gJWP5Vedpo9tq 4qVSd3U8ekGWk7J1a+epmq4njaCFBVzfftewuSVMvwcXlLxg/YffbTA8py07j6pDfb ImDWFwJ6dv5ww== From: Sasha Levin To: stable@vger.kernel.org Cc: Jeff Layton , stable@kernel.org, Nicholas Carlini , Chuck Lever , Sasha Levin Subject: [PATCH 5.15.y] nfsd: fix heap overflow in NFSv4.0 LOCK replay cache Date: Fri, 20 Mar 2026 07:39:41 -0400 Message-ID: <20260320113941.3971332-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2026032010-shredding-stargazer-b481@gregkh> References: <2026032010-shredding-stargazer-b481@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Jeff Layton [ Upstream commit 5133b61aaf437e5f25b1b396b14242a6bb0508e2 ] 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 Tested-by: Nicholas Carlini Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever [ replaced `op_status_offset + XDR_UNIT` with existing `post_err_offset` variable ] Signed-off-by: Sasha Levin --- 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 46a7fd731ba0a..e02c5650e2ac4 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -5439,9 +5439,14 @@ 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: *p = op->status; diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h index 477828dbfc665..53298bdcfb3d0 100644 --- a/fs/nfsd/state.h +++ b/fs/nfsd/state.h @@ -430,11 +430,18 @@ 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 -- 2.51.0