From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 5E558471255; Tue, 21 Jul 2026 18:09:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657384; cv=none; b=UtOIjb/fppd3F4EI12mO+DMLg/kugNQUAPotxdDhKFeRGRDylE5Vqy3GUcrFbMTHHH8D15UmfjfKJU681t9ug45Msj656VlOuJmk5bv2dtjY+h7dGfNDqdKDr8OxNQZXa/2FGA1TvBsC4k4bXwXfnIqpRKmaU6J3ndtL1wR23+0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784657384; c=relaxed/simple; bh=RO/d+u4eZQqsv82HggfnQnwvVVvm40kSl+HgcQ53ceo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RyoARXTeXuwg+/rTxjQmy+0vHjJoejCVJfje1zxKszCQ3cMekrFFY2RJ2Q4GtzUa16D8HoKNdUu+jjfUYO6S4nADx72Irrg0HG0gPXobSRyjgtFvQMwdmLyYe5QR6gE8CIxr1eP7XDJtXFnniMOjpmdzk4WSWthOk0QjcZJaStE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Fe7gRzJP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Fe7gRzJP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 89B4D1F000E9; Tue, 21 Jul 2026 18:09:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784657383; bh=0GwfCcaDCRTumaGv4A8rGYIkhoWgxVyK4IZ//Cuw30g=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=Fe7gRzJP1V38mabDzlS+KByXrV/laE+zeQ/GLEItvTjtHnagCgtOazz1IHT2txjxk q4SI7/1SbW6AP9G9RwqNrox78wyQyapQZI2lOyjvXAp/EqWPzyJO4gCTX4wgZCKRrZ KkpljGO7UMONE/HUl7bAI4hZvSUJXnYrAU5QSM5Y= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Chuck Lever , Anna Schumaker , Sasha Levin Subject: [PATCH 6.18 0701/1611] xprtrdma: Fix bcall rep leak and unbounded peek Date: Tue, 21 Jul 2026 17:13:37 +0200 Message-ID: <20260721152531.148000666@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152514.750365251@linuxfoundation.org> References: <20260721152514.750365251@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason [ Upstream commit c7653d5cebc8492c77ec0415b5e9c0fb3e644bc6 ] rpcrdma_is_bcall() decodes a reply's first words to decide whether the frame is a backchannel call. Two issues in that decode path let a short or malformed reply leak the receive buffer and drain the Receive queue. First, the speculative peek p = xdr_inline_decode(xdr, 0); /* five p++ reads follow */ asks xdr_inline_decode() for zero bytes, which returns xdr->p without consulting xdr->end. The five subsequent __be32 reads can then walk up to 20 bytes past the wire payload into stale regbuf contents and misclassify the reply as a backchannel call. Second, after the post-peek p = xdr_inline_decode(xdr, 3 * sizeof(*p)); if (unlikely(!p)) return true; the short-header arm returns true without calling rpcrdma_bc_receive_call(). The contract with the caller is that a true return transfers ownership of rep to the backchannel path: rpcrdma_reply_handler() if (rpcrdma_is_bcall(r_xprt, rep)) return; /* bare return, skips out_post */ ... out_post: rpcrdma_post_recvs(r_xprt, credits + ...); Because rpcrdma_bc_receive_call() never ran, no one took rep, but rpcrdma_reply_handler still bare-returns past rpcrdma_rep_put() and rpcrdma_post_recvs(). The rep, with its persistently DMA-mapped receive buffer, is orphaned on rb_all_reps and freed only at transport teardown. This completion reposts nothing, so its slot is reclaimed only when a later forward-channel reply reaches out_post and rpcrdma_post_recvs() allocates a fresh rep to backfill; absent that traffic the Receive queue drains and the peer's Sends draw RNR NAKs. Fix by consulting xdr->end after the zero-length peek so the five __be32 reads cannot run unless 20 bytes of wire payload remain. A byte-precise comparison against xdr->end is required because a non-4-aligned receive rounds the stream's word count up past the true payload. Also return false from the short-header arm so the reply falls through the normal out_norqst cleanup chain (rpcrdma_rep_put() plus rpcrdma_post_recvs()). Fixes: 41c8f70f5a3d ("xprtrdma: Harden backchannel call decoding") Assisted-by: kres:claude-opus-4-7 Signed-off-by: Chris Mason Signed-off-by: Chuck Lever Signed-off-by: Anna Schumaker Signed-off-by: Sasha Levin --- net/sunrpc/xprtrdma/rpc_rdma.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c index fb65afb44d9002..d19e371d63cf1a 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -1133,6 +1133,8 @@ rpcrdma_is_bcall(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep) /* Peek at stream contents without advancing. */ p = xdr_inline_decode(xdr, 0); + if ((char *)xdr->end - (char *)p < 5 * XDR_UNIT) + return false; /* Chunk lists */ if (xdr_item_is_present(p++)) @@ -1157,7 +1159,7 @@ rpcrdma_is_bcall(struct rpcrdma_xprt *r_xprt, struct rpcrdma_rep *rep) */ p = xdr_inline_decode(xdr, 3 * sizeof(*p)); if (unlikely(!p)) - return true; + return false; rpcrdma_bc_receive_call(r_xprt, rep); return true; -- 2.53.0