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 333593515D5 for ; Thu, 3 Sep 2026 14:31:50 +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=1788445919; cv=none; b=ipnqT+VWy1Tn9LuNLnuc4+bf0k+UnwtFPA8rUib4KkdcXdtK60S33f0ug1HyIjHIkajFWuNgaFlgTIheStO/k4atzeB/f9LosnXjTVPauXiKMVHPRzHS63enWmtWRD3ILeyK11V76j2p/q732y/vtTmjg7BRcIlBcZTv6gG9cvI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788445919; c=relaxed/simple; bh=bG/YOmJbDiE9Vma0rYwZq3tqWM2VoNjMdaFSXcNq/Q4=; h=Subject:To:Cc:From:Date:Message-ID:MIME-Version:Content-Type; b=kiPArAndqZ/0dNLaFTRNIsLqQL6ZKmmTPRkNGlj+nQ7eVmWXPD0KbuIiSVZ8GbrayDYHLx62EC8jXwEWHPphmN/d1yZXGDsZaB8b6EzAUOMHlhybFXpopVZ6GIyXHrHVm3z8gY7kxJeX62u/US70/iBDd6uT0Ps69E+8+7HPnlc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=l/lQInWp; 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="l/lQInWp" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6FC921F000E9; Thu, 3 Sep 2026 14:31:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788445909; bh=F6HBVdy73keeJa8+5Lx5T1eBva3tabBIn3JO2xzZpq4=; h=Subject:To:Cc:From:Date; b=l/lQInWpR4Hu6JvyQL4ljVs1dy0k2IxWCZVbA+QvRHf/TuN1IT83Zu5t4mrHd9+/a rKVBlI1JmD+DmlTV+nR4Nt7L33kQy/DKhpzBl9xFDC1dqN5CXCASzG8MzV/61qcLmV zKz+eN+Dp2LqLr63zjBj8kgsuc33jC/b/albtaso= Subject: FAILED: patch "[PATCH] svcrdma: Reject Write/Reply chunks with segcount 0" failed to apply to 6.12-stable tree To: clm@meta.com,chuck.lever@oracle.com,jlayton@kernel.org Cc: From: Date: Thu, 03 Sep 2026 16:10:42 +0200 Message-ID: <2026090342-canary-synopses-a220@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 9808eb7656666acc7291bae9ab6b987bd16e47e0 # git commit -s git send-email --to '' --in-reply-to '2026090342-canary-synopses-a220@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From 9808eb7656666acc7291bae9ab6b987bd16e47e0 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Tue, 26 May 2026 09:35:59 -0400 Subject: [PATCH] svcrdma: Reject Write/Reply chunks with segcount 0 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 diff --git a/net/sunrpc/xprtrdma/svc_rdma_pcl.c b/net/sunrpc/xprtrdma/svc_rdma_pcl.c index 1f8f7dad8b6f..18d1045799ce 100644 --- 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_recv_ctxt *rctxt, 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_recv_ctxt *rctxt, chunk->ch_length += segment->rs_length; chunk->ch_segcount++; } + list_add_tail(&chunk->ch_list, &pcl->cl_chunks); } return true; } diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index 15c1d8ae5301..f6a7533a7555 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -510,10 +510,13 @@ static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt) 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,