From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender-op-o17.zoho.eu (sender-op-o17.zoho.eu [136.143.169.17]) (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 2FA62399002; Mon, 20 Jul 2026 17:08:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.169.17 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784567288; cv=pass; b=d+oPIZybu+5iC30c3rrn9bDSMhfODwWHDipaIAcau6hKLbzgfSNjRp6ro+aAXF5KGhTzzk8lcwSVztlbmR7Tg5yYDm2Hut9s0NFuC6jsoSEvx0qEjv1sFplO1W8nt2eSpmFg8jXMTieFG87JPLUY8KYwRd2Qux9TId6zpKo5XmQ= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784567288; c=relaxed/simple; bh=dNqVxR63V6xQon7zsJn+Ma77TefGiYPz54fRdZ8GDJc=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=e/gveVBHrHY7M0P1E2GvI8flibGhKE89YKwy6SVJAgsPZ2wHw2J0z0X9OO59Yrrv5lfpsywx3H7qvJ+fcb//fhezKd4NcCACx7H5lcH8DfPBaXeubkLTNYudbynkUjm8fQfJ/zhRwTSL1H0VcMkN41ZiGyls6HR8zxWO5rHGW/g= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=auditcode.ai; spf=pass smtp.mailfrom=auditcode.ai; dkim=pass (1024-bit key) header.d=auditcode.ai header.i=security@auditcode.ai header.b=ku50Hzrc; arc=pass smtp.client-ip=136.143.169.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=auditcode.ai Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=auditcode.ai Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=auditcode.ai header.i=security@auditcode.ai header.b="ku50Hzrc" ARC-Seal: i=1; a=rsa-sha256; t=1784567244; cv=none; d=zohomail.eu; s=zohoarc; b=ld8knbAu/Ah1xIom4ITHvPesNMHjfsXzJ6OSFIiwQ+SJtXvZ7KGOalBfVX5K5JrXMPtOtlefZbJjfFJQrfl9lxEjk/UMA1tMSm8FhtZUg21e8yadLJLldLNv69FVLcAFQAZswIBPzfIX0wLlKjxLGHAjt663gVf5g4TO+lFe3qk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.eu; s=zohoarc; t=1784567244; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:MIME-Version:Message-ID:Subject:Subject:To:To:Message-Id:Reply-To; bh=HjByz5AvHsIQNltISoR9+2X9Bmm/qrLTUWsUjkq8GY8=; b=UDLZFinvllHs7jIEOTFx3rgQyruEbU1oRT86rjUmiKFp4SqSjQzBd59EgkEeE0yuS8vLT73c86GsLLJrt10sH9OoY3jz2wRCWM8WLrSOodqQXRleKWPTSIQbN8KJtiIm5h/hYeAPn8oQ+g8GZPVcQPWvYoGGvy9UT+GLFZUYNro= ARC-Authentication-Results: i=1; mx.zohomail.eu; dkim=pass header.i=auditcode.ai; spf=pass smtp.mailfrom=security@auditcode.ai; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1784567244; s=zmail; d=auditcode.ai; i=security@auditcode.ai; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:MIME-Version:Content-Transfer-Encoding:Message-Id:Reply-To; bh=HjByz5AvHsIQNltISoR9+2X9Bmm/qrLTUWsUjkq8GY8=; b=ku50Hzrc4DRQ5WqQiTWRTVI3Hz5nicabKWCgmkKJzz42FlWsfpR4Dri6xvjY+Dwd jdbOryCN4+SaRReYpsFYXLqunJRAVR5qgc9rWL4THGzInUtGx/ACQ68Jg/vrQkVX7hK pQ9CB7EptjY9KemObm931E07X9lKbfGCidG2IdHI= Received: by mx.zoho.eu with SMTPS id 1784567241224482.3073788218354; Mon, 20 Jul 2026 19:07:21 +0200 (CEST) From: Ibrahim Hashimov To: alibuda@linux.alibaba.com, dust.li@linux.alibaba.com, wenjia@linux.ibm.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: tonylu@linux.alibaba.com, guwen@linux.alibaba.com, horms@kernel.org, linux-rdma@vger.kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net] net/smc: validate peer CDC cursor against RMBE size before accepting it Date: Mon, 20 Jul 2026 19:07:17 +0200 Message-ID: <20260720170717.11425-1-security@auditcode.ai> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External smc_cdc_cursor_to_host() converts the wire-format producer/consumer cursor of an incoming CDC message into a host smc_host_cursor. It rejects a cursor that goes backwards, but never checks that the cursor's count is inside the buffer it indexes. Per smc_host_cursor ("an offset in an RMBE") and the invariant smc_curs_add() enforces for every local advance (0 <= count < size), a valid cursor count must be < size; the wire cursor is peer-controlled and was never checked against that. smcr_cdc_msg_to_host() accepts the producer and consumer cursors, and the unbounded value feeds smc_curs_diff() in smc_cdc_msg_recv_action(), which computes new->count - old->count without clamping against size. A peer that puts an out-of-range prod.count on the wire (e.g. 0x7fffffff) drives bytes_to_rcv far past rmb_desc->len -- the very invariant the comment above the atomic_add() claims but does not enforce. smc_rx_recvmsg() then trusts bytes_to_rcv as the amount of valid RMB data. Its first copy chunk is safely bounded by rmb_desc->len - cons.count, but the second chunk copies (copylen - chunk_len) bytes from offset 0, and copylen came from the inflated readable -- an out-of-bounds read of the RMB's backing (v)malloc allocation, copied straight to the receiving process via _copy_to_iter(). This is a remote kernel-memory disclosure driven by a malicious SMC-R peer, needing no local privilege on the victim. The same unbounded count also reaches smc_cdc_handle_urg_data_arrival() (base + urg_curs.count - 1) -- a second, narrower OOB read. Fix it where the wire cursor is accepted, mirroring the cursor-sanity idiom two lines above: reject any incoming cursor whose count is >= the size of the buffer it will index. smc_cdc_cursor_to_host() gains a size parameter; smcr_cdc_msg_to_host() passes conn->rmb_desc->len for the producer cursor and conn->peer_rmbe_size for the consumer cursor. This bounds it at its single origin instead of patching every downstream consumer. SMC-D (smcd_cdc_msg_to_host()) does not use this helper and is a separate, out-of-scope gap. Reproduced on a v6.19 KASAN kernel (SMC-Rv2 over soft-RoCE): a peer emitting prod.count=0x7fffffff triggers a vmalloc-out-of-bounds read in _copy_to_iter() via smc_rx_recvmsg(), returning ~960 KB of RMB-adjacent kernel heap to userspace; an in-range cursor transfers cleanly. With the fix the out-of-range cursor is dropped before it reaches conn->local_rx_ctrl.prod, and the reproducer returns rc=0 with no report. Fixes: 5f08318f617b ("smc: connection data control (CDC)") Cc: stable@vger.kernel.org Signed-off-by: Ibrahim Hashimov Assisted-by: AuditCode-AI:2026.07 --- net/smc/smc_cdc.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/net/smc/smc_cdc.h b/net/smc/smc_cdc.h index 696cc11f2303..f07bbef47073 100644 --- a/net/smc/smc_cdc.h +++ b/net/smc/smc_cdc.h @@ -221,6 +221,7 @@ static inline void smc_host_msg_to_cdc(struct smc_cdc_msg *peer, static inline void smc_cdc_cursor_to_host(union smc_host_cursor *local, union smc_cdc_cursor *peer, + unsigned int size, struct smc_connection *conn) { union smc_host_cursor temp, old; @@ -235,6 +236,14 @@ static inline void smc_cdc_cursor_to_host(union smc_host_cursor *local, if ((old.wrap == temp.wrap) && (old.count > temp.count)) return; + /* count is an offset into the RMBE and must always stay inside + * it (see smc_curs_add()); the peer is untrusted, so reject an + * out-of-range wire cursor the same way an out-of-order one is + * already rejected above, instead of letting it drive + * bytes_to_rcv / the urgent-byte offset past the buffer end + */ + if (temp.count >= size) + return; smc_curs_copy(local, &temp, conn); } @@ -246,8 +255,10 @@ static inline void smcr_cdc_msg_to_host(struct smc_host_cdc_msg *local, local->len = peer->len; local->seqno = ntohs(peer->seqno); local->token = ntohl(peer->token); - smc_cdc_cursor_to_host(&local->prod, &peer->prod, conn); - smc_cdc_cursor_to_host(&local->cons, &peer->cons, conn); + smc_cdc_cursor_to_host(&local->prod, &peer->prod, + conn->rmb_desc->len, conn); + smc_cdc_cursor_to_host(&local->cons, &peer->cons, + conn->peer_rmbe_size, conn); local->prod_flags = peer->prod_flags; local->conn_state_flags = peer->conn_state_flags; } -- 2.50.1 (Apple Git-155)