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 CCA1430C366; Fri, 4 Sep 2026 05:52:04 +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=1788501126; cv=none; b=SlffzTL0Pbv35kXS4akeOls8fTVYOOMMomPibyiUNQzuKDIPplL5Ju/iE/fdhEDZW/rd4tDlLfqUiUTBOyvEl67ciHZj8KDpOTGNyrL2tEUx0MRYAIdDlSuZpd52Gmnp4x2DbuaSKjeQ547o/CF7czf0N3ER/6z0ASe4EUKvHVg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788501126; c=relaxed/simple; bh=O7NaSAZYbprhDvjBOcDkPTFKxZAOnXkg+PtcdmgshZM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=VcEYplIa7HKTAuTTI1m8i8sFmqXmwukxgiJ9LhHsTqtJmdePC8qSeNkSYlOwWQCcJ5VUwOh4XJvCdK99FFWHeiv9E1nn1S8JT3KKCuE7J+BXUwGh6sasfi/YrNv7a1mZSavVnsCs4qPJg3ZlqZH/1KbfRwBDu9F9rrjdJ9X+9dc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1j+v3q2b; 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="1j+v3q2b" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33D051F00A3D; Fri, 4 Sep 2026 05:52:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788501124; bh=VJS2ZV9s3A0dLvACxU97nkM6U+VPvjJzRJV0zXvWBAs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=1j+v3q2bTr1/W7F6lJj4omY+1Y2WhFtsOBivS4cKJ+btRiS8mgNfSuKMf945bA2x+ 4WwuQjSI0T8DkMCRwa4Z6b5IeQ4nHG8S7dMA5g/UQG7bsfS8qpGYSXvsqdtv9SsqaZ EosPEhZzlWjyNFn+UCX3dtJi9A2F+SnnB3GBhS3M= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chris Mason , Jeff Layton , Chuck Lever Subject: [PATCH 6.18 297/552] svcrdma: Reject Write/Reply chunks with segcount 0 Date: Fri, 4 Sep 2026 06:57:34 +0200 Message-ID: <20260904045756.816662861@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260904045747.813364717@linuxfoundation.org> References: <20260904045747.813364717@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 commit 9808eb7656666acc7291bae9ab6b987bd16e47e0 upstream. A peer can send a Write or Reply chunk whose segcount field is zero. xdr_check_write_chunk() only rejects segcount > rc_maxpages, so zero passes the range check, and xdr_inline_decode(stream, 0) returns the current (non-NULL) cursor without advancing. The function returns true and pcl_alloc_write() then links a struct svc_rdma_chunk with ch_segcount == 0 onto rc_write_pcl or rc_reply_pcl. An earlier patch in this series made pcl_for_each_segment() safe for ch_segcount == 0, so this no longer drives the memory walk it used to. Rejecting the malformed frame at the decode boundary is still worthwhile as defense in depth: it keeps degenerate zero-segment chunks off the parsed chunk lists entirely, so any future consumer that walks ch_segments directly cannot observe one, and it makes the zero-floor easy to backport to trees where the macro change is more intrusive. RFC 8166 has no meaning for a Write/Reply chunk that describes no remote buffer, so no legitimate client is affected. xdr_check_reply_chunk() funnels Reply chunks through xdr_check_write_chunk() and inherits the same rejection. pcl_alloc_write() also links each chunk onto the parsed chunk list before filling its segment array. If a future change weakens the segcount-0 rejection, an incomplete chunk is visible to consumers during the fill loop. Reorder so that list_add_tail() follows the segment fill loop, ensuring only fully-populated chunks appear on the list. Fixes: 78147ca8b4a9 ("svcrdma: Add a "parsed chunk list" data structure") Cc: stable@vger.kernel.org Assisted-by: kres (claude-opus-4-7) Signed-off-by: Chris Mason Acked-by: Jeff Layton Link: https://patch.msgid.link/20260526-rpc-kernel-bugs-v1-5-e251306ccca9@oracle.com Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/xprtrdma/svc_rdma_pcl.c | 2 +- net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 9 ++++++--- 2 files changed, 7 insertions(+), 4 deletions(-) --- a/net/sunrpc/xprtrdma/svc_rdma_pcl.c +++ b/net/sunrpc/xprtrdma/svc_rdma_pcl.c @@ -213,7 +213,6 @@ bool pcl_alloc_write(struct svc_rdma_rec chunk = pcl_alloc_chunk(segcount, 0); if (!chunk) return false; - list_add_tail(&chunk->ch_list, &pcl->cl_chunks); for (j = 0; j < segcount; j++) { segment = &chunk->ch_segments[j]; @@ -225,6 +224,7 @@ bool pcl_alloc_write(struct svc_rdma_rec chunk->ch_length += segment->rs_length; chunk->ch_segcount++; } + list_add_tail(&chunk->ch_list, &pcl->cl_chunks); } return true; } --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -498,10 +498,13 @@ static bool xdr_check_write_chunk(struct return false; /* Before trusting the segcount value enough to use it in - * a computation, perform a simple range check. This is an - * arbitrary but sensible limit (ie, not architectural). + * a computation, perform a simple range check. A zero + * segcount describes no remote buffer and is rejected so + * downstream consumers never see a degenerate ch_segcount==0 + * chunk. The upper bound is an arbitrary but sensible limit + * (ie, not architectural). */ - if (unlikely(segcount > rctxt->rc_maxpages)) + if (segcount == 0 || unlikely(segcount > rctxt->rc_maxpages)) return false; p = xdr_inline_decode(&rctxt->rc_stream,