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 ACBDC315D33; Thu, 2 Jul 2026 16:41:14 +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=1783010475; cv=none; b=qpf7FWJeyAgk8PG4WAfhRwJC4/2yTD2N7xoHP1Rwg2IWthgN6zx4qMBl5RgYgVivk4t8BX0zVWR2tL84JwHFPozWICvE/YO+hCt562+hAK5INUketKdE20nPFWgKPB0RTGNFIQc4w5Y6YyDc+3QdEiyxzZjJby6Udn7J4jhZ480= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783010475; c=relaxed/simple; bh=AbQJEcEwbN0Bf3/0+hZLeZv+pGsX2P8oe9+HCO09iUo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=FSMcrRyaXRbw68tyKwbh27yzDgSBk8b2fOGN8u4+t1T/3TDP87FGSFDU/3jPEi+H1Zma493HulRfsBlyQsPtgLr1yxe2rWBB9Z0azZtLSy+s6gGUQ0mXAtkzX8K5WHpa1AZeoCIbuM2kC5kDJnnUloKdF8xKeCDcKismmMDIPzU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=eU4r0BZT; 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="eU4r0BZT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DFBC1F000E9; Thu, 2 Jul 2026 16:41:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1783010474; bh=s4uu0yOYEF2ChVeSiadU+PIy/gGQKqgtSXsbtYL8O9s=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=eU4r0BZTV2TQEUBw0oLQzVYpYYucwnoytxhEdptkAiuWMYZt67oKc/Lifz+HNPWbK mtqbYL4g5sJFWmfXkt3wRre52XSRx6/+Z6Nw7lUXj4IxoHhnzOErEm7fNoGwcm1PWw uiFP5oV7TnBT3VEPIc0t/jRX5Q23IyJtDkzGC4eE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jungwoo Lee , Wongi Lee , Ido Schimmel , Jakub Kicinski Subject: [PATCH 6.12 124/204] ipv6: account for fraggap on the paged allocation path Date: Thu, 2 Jul 2026 18:19:41 +0200 Message-ID: <20260702155121.256927670@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260702155118.667618796@linuxfoundation.org> References: <20260702155118.667618796@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 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Wongi Lee commit 736b380e28d0480c7bc3e022f1950f31fe53a7c5 upstream. In __ip6_append_data(), when the paged-allocation branch is taken (MSG_MORE / NETIF_F_SG / large fraglen), alloclen and pagedlen are computed as alloclen = fragheaderlen + transhdrlen; pagedlen = datalen - transhdrlen; datalen already includes fraggap (datalen = length + fraggap). When fraggap is non-zero, this is not the first skb and transhdrlen is zero. The fraggap bytes carried over from the previous skb are copied just past the fragment headers in the new skb's linear area. The linear area is therefore undersized by fraggap bytes while pagedlen is overstated by the same amount, and the copy writes past skb->end into the trailing skb_shared_info. An unprivileged user can trigger this via a UDPv6 socket using MSG_MORE together with MSG_SPLICE_PAGES. The bad accounting was introduced by commit 773ba4fe9104 ("ipv6: avoid partial copy for zc"). Before commit ce650a166335 ("udp6: Fix __ip6_append_data()'s handling of MSG_SPLICE_PAGES"), the negative copy value caused -EINVAL to be returned. That later commit allowed MSG_SPLICE_PAGES to proceed in this case, making the corruption triggerable. The non-paged branch sets alloclen to fraglen, which already accounts for fraggap because datalen does. Bring the paged branch in line by adding fraggap to alloclen and subtracting it from pagedlen. After this adjustment, copy no longer collapses to -fraggap on the paged path, so remove the stale comment describing that old arithmetic. Since a negative copy is no longer expected for a valid MSG_SPLICE_PAGES case, remove the MSG_SPLICE_PAGES exception from the negative copy check. Fixes: 773ba4fe9104 ("ipv6: avoid partial copy for zc") Signed-off-by: Jungwoo Lee Signed-off-by: Wongi Lee Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/ajFTqRljatR17fFy@DESKTOP-19IMU7U.localdomain Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/ipv6/ip6_output.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -1633,8 +1633,8 @@ alloc_new_skb: !(rt->dst.dev->features & NETIF_F_SG))) alloclen = fraglen; else { - alloclen = fragheaderlen + transhdrlen; - pagedlen = datalen - transhdrlen; + alloclen = fragheaderlen + transhdrlen + fraggap; + pagedlen = datalen - transhdrlen - fraggap; } alloclen += alloc_extra; @@ -1649,10 +1649,7 @@ alloc_new_skb: fraglen = datalen + fragheaderlen; copy = datalen - transhdrlen - fraggap - pagedlen; - /* [!] NOTE: copy may be negative if pagedlen>0 - * because then the equation may reduces to -fraggap. - */ - if (copy < 0 && !(flags & MSG_SPLICE_PAGES)) { + if (copy < 0) { err = -EINVAL; goto error; }