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 624F639A07C; Wed, 23 Sep 2026 14:36:22 +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=1790174183; cv=none; b=ZnYxUgoCR44R1LEo+J07Q73rS6lSP2FLm3cwpWUUMulRQRthlEMQEXGpshQez1LB/wfoZE/3txkyj3zepiTYf9EDoy7TaBVYAz3+nKmZBcLBwT4eKVuzmoroEh0+E1ywZR7BGZsdva9U7zxjH0pN/bAyMVZQUMxH1dkKtn4S2pQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790174183; c=relaxed/simple; bh=a8T0r46XbJSAQWBhCngVE+e170kOrOk5STa91761XHY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rF0UfbjoeH9ys0qJPhUe/e4WusY0pvYPD0KRQHRDmupxgdR9smyLzNUZOYiwSb/At4J/HVrh+lvuk8SPPlf2eu3KLXY1P/1wa5TVwBx1BNGX93V2vn7d31WsuQAVkhlSVUoa06fQPFYp8Z2GohOUPZrdTPdIafcXEYEqoWDeQnY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=V9dYFw8I; 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="V9dYFw8I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7064F1F00893; Wed, 23 Sep 2026 14:36:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1790174182; bh=goiFT7jU8Y1qmGVf3J1XNlGwE5v3Ix1+xrNvJN1xQqA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=V9dYFw8IVIXxCVbktyqQDq4XcSfzcD8boMoxKr1LNuJidP4kFKRXDU/1ypnMaDpyg 9dTflwcAICGoCIc60s5KivHu8l5pjSwqOfkKQTA9uWt1DdC+yV7opheea/fqSkYTdk 1QifaKLKail66j9r59cUtyAVmASMfB3pfGo72Szw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Roshan Kumar , Steffen Klassert , Sasha Levin Subject: [PATCH 6.18 017/398] xfrm: iptfs: fix stack OOB read in iptfs_skb_reset_frag_walk() Date: Wed, 23 Sep 2026 16:01:31 +0200 Message-ID: <20260923140643.884769624@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260923140643.441954610@linuxfoundation.org> References: <20260923140643.441954610@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: Roshan Kumar [ Upstream commit d042487dc118e494db2e2c1382310255c90ff544 ] iptfs_skb_reset_frag_walk() advances to the fragment containing @offset with an unbounded loop: while (offset >= walk->past + walk->frags[walk->fragi].len) walk->past += walk->frags[walk->fragi++].len; walk->fragi is advanced and walk->frags[walk->fragi] is dereferenced without ever checking fragi against walk->nr_frags. When the requested offset is at or beyond the total length spanned by the walk's fragments, fragi runs past nr_frags and off the end of the fixed-size on-stack frags[MAX_SKB_FRAGS + 1] array, reading out-of-bounds stack memory. The two callers behave differently: iptfs_skb_add_frags() already guards against this with if (!walk->nr_frags || offset >= walk->total + walk->initial_offset) return len; but iptfs_skb_can_add_frags() has no such guard and calls iptfs_skb_reset_frag_walk() unconditionally, so it performs the out-of-range walk. Its own "fragi < walk->nr_frags" bound check runs only afterwards, too late to prevent the read. This is reachable from the receive path: a crafted IP-TFS (AGGFRAG) payload delivered to an IPTFS SA drives iptfs_reassem_cont() -> iptfs_skb_can_add_frags() with an offset past the fragment total, e.g.: BUG: KASAN: stack-out-of-bounds in iptfs_skb_reset_frag_walk+0x235/0x250 Read of size 4 at addr ffff888008ad7210 by task repro/345 iptfs_skb_reset_frag_walk+0x235/0x250 net/xfrm/xfrm_iptfs.c:392 iptfs_skb_can_add_frags+0x155/0x310 net/xfrm/xfrm_iptfs.c:420 iptfs_reassem_cont+0xcf8/0x1140 net/xfrm/xfrm_iptfs.c:902 iptfs_input_ordered+0x552/0x670 net/xfrm/xfrm_iptfs.c:1280 iptfs_input+0x3d6/0xde0 net/xfrm/xfrm_iptfs.c:1741 xfrm_input+0x282f/0x6140 net/xfrm/xfrm_input.c:700 xfrm4_esp_rcv+0x93/0x120 net/ipv4/xfrm4_protocol.c:104 ip_rcv+0x278/0x2d0 net/ipv4/ip_input.c:612 Give iptfs_skb_can_add_frags() the same up-front guard that iptfs_skb_add_frags() already has, so the walk is never entered with an out-of-range offset. When it triggers, the caller falls back to the existing linearize-and-copy path, which is safe. Fixes: 5f2b6a909574 ("xfrm: iptfs: add skb-fragment sharing code") Reported-by: Roshan Kumar Signed-off-by: Roshan Kumar Signed-off-by: Steffen Klassert Signed-off-by: Sasha Levin --- net/xfrm/xfrm_iptfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/net/xfrm/xfrm_iptfs.c b/net/xfrm/xfrm_iptfs.c index d39253b06c4ef..0f562301ceb34 100644 --- a/net/xfrm/xfrm_iptfs.c +++ b/net/xfrm/xfrm_iptfs.c @@ -416,6 +416,14 @@ static bool iptfs_skb_can_add_frags(const struct sk_buff *skb, if (skb_has_frag_list(skb) || skb->pp_recycle != walk->pp_recycle) return false; + /* Reject an @offset that is at or beyond the end of the walk's data + * before calling iptfs_skb_reset_frag_walk(), whose fragment-advance + * loop is otherwise unbounded and would index past walk->frags[]. + * This mirrors the guard already present in iptfs_skb_add_frags(). + */ + if (!walk->nr_frags || offset >= walk->total + walk->initial_offset) + return false; + /* Make offset relative to current frag after setting that */ offset = iptfs_skb_reset_frag_walk(walk, offset); -- 2.53.0