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 859343C3F6A for ; Wed, 19 Aug 2026 19:08:43 +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=1787166524; cv=none; b=JX/7ZKtguL2hFnRq20HWmjZf50zLEYvChkBjPyfReM++n3uAE0u+gIjmW19iU6WP4OsxsjdPpSvQgY9OtzGOQZ/k5/FNWFN7LY582b+Rx7AwNRzt9/5ADbgpE2du0QJDt9qmjxKvxyzS00IbBL+WxOdIgZ4EgH5Vx5JD/BlK6t8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787166524; c=relaxed/simple; bh=5L/erPvlrzRevbeS960ba66iYawh/iBGuRmzhAEDeOE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=rQgG3+LX9HqVoxg3zC9UpVn42l3V7qs5KGyS1Dx2PJRibkQhkkqgKBgSAnTGzAC5JC0lb/bqBgVzhwuvIGkjU5/Ug36KNqLUYwKxPxrPbl3hWlvgd1W9syzMxj+SpzOgeCsc9qCGeS+K2ysSzryfrmVtci5plmWA3O0UtQaqYNQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kYcYBx+J; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kYcYBx+J" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98FCF1F00A3D; Wed, 19 Aug 2026 19:08:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787166523; bh=nNZEA914Uz0FgYCaWYO8zC6wx0jYK+qHNytMDe9Nr3U=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=kYcYBx+JI2DA14uc2wOxI9cUKU0yuJjnBeeZRBngpxmL6NBpWY7DQfHGTKmLzANK+ zJBOoNoc5ax/DkSsiMfJvv/7491iPF1pzHFzsfFqysoHRlk7UTVEVoamI2rqREcRgp 2bkljo8Zd2FxqWv6KdjrsbidizX+oL067vXrdIKL9X20kUHUtwai+PjtjLjunU1Fl4 HvCXkKKSqpFl06pj3k5FQiV8kkQu6lVyK9Bbypr0fJmbIiLAc4jC32d0fKTgXwRf4L gRhZXvga1DQJ3DUAEY4d/o1j09Lox5gYe7HBUyvzrGcq/Sv8bg9LPjz+4YFGUpUblT azS0sodMy73XQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Hyunjung Ko , Jamal Hadi Salim , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1.y 4/4] net/sched: act_ct: fix sk_buff leak when the header checks reject a packet Date: Wed, 19 Aug 2026 15:08:36 -0400 Message-ID: <20260819190836.561493-4-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260819190836.561493-1-sashal@kernel.org> References: <2026081753-suffix-dill-686c@gregkh> <20260819190836.561493-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Hyunjung Ko [ Upstream commit 8a7ed561671aa6a911a2de99e59ef670a4d0b1df ] tcf_ct_handle_fragments() runs its header sanity checks before handing anything to the defragmentation engine: if (family == NFPROTO_IPV4) err = tcf_ct_ipv4_is_fragment(skb, &frag); else err = tcf_ct_ipv6_is_fragment(skb, &frag); if (err || !frag) return err; tcf_ct_ipv4_is_fragment() returns -EINVAL or -ENOMEM; tcf_ct_ipv6_is_fragment() adds -EPROTO when ipv6_find_hdr() fails. None of them frees or queues the skb, so on that path the caller still owns it. tcf_ct_act() however funnels every non-zero return into the ownership-transfer exit: err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag); if (err) goto out_frag; ... out_frag: if (err != -EINPROGRESS) tcf_action_inc_drop_qstats(&c->common); return TC_ACT_CONSUMED; TC_ACT_CONSUMED means the action took ownership of the skb, so no caller frees it - sch_handle_ingress(), sch_handle_egress() and tcf_qevent_handle() all deliberately skip the free for that verdict. The skb is therefore orphaned: one sk_buff plus its data buffer is leaked per malformed packet, unbounded. Note the drop counter is already incremented for these errors, so the statistics claim a drop that never happens. Three different ownership states reach out_frag: today - the skb may be queued by the defrag engine (-EINPROGRESS), already freed by nf_ct_handle_fragments(), or still owned by us. Tell the caller which of those it is, and free the packet ourselves in the last case, which restores the TC_ACT_SHOT behaviour that predated the Fixes: commit. Reproduced on v7.2-rc6 with a 54-byte frame carrying a 40-byte IPv6 header with nexthdr = 0 (hop-by-hop) and nothing after it, on a clsact ingress chain with "action ct". kmemleak reports one leaked 232-byte skbuff_head_cache object plus its 704-byte data buffer per packet; with this patch it reports none. Fixes: 3f14b377d01d ("net/sched: act_ct: fix skb leak and crash on ooo frags") Cc: stable@vger.kernel.org # v6.8+ Signed-off-by: Hyunjung Ko Acked-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260806101235.809370-1-hj351016@gmail.com Signed-off-by: Jakub Kicinski [ Dropped upstream's `bool add_helper = false;` context line, absent on 6.1, keeping only the new `bool skb_is_ours = false;` declaration. ] Signed-off-by: Sasha Levin --- net/sched/act_ct.c | 29 +++++++++++++++++++++++++---- 1 file changed, 25 insertions(+), 4 deletions(-) diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c index 81c023f8433cc..f6b2f693e21d5 100644 --- a/net/sched/act_ct.c +++ b/net/sched/act_ct.c @@ -854,8 +854,15 @@ static int tcf_ct_ipv6_is_fragment(struct sk_buff *skb, bool *frag) return 0; } +/* On error, tells the caller whether it still owns @skb and must free it + * itself. @skb is ours only when the header checks below reject the packet + * before it is handed to the defragmentation engine; once nf_ct_handle_ + * fragments() has been called the skb is either queued (-EINPROGRESS) or has + * already been freed by it. + */ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb, - u8 family, u16 zone, bool *defrag) + u8 family, u16 zone, bool *defrag, + bool *skb_is_ours) { enum ip_conntrack_info ctinfo; struct nf_conn *ct; @@ -872,8 +879,12 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb, err = tcf_ct_ipv4_is_fragment(skb, &frag); else err = tcf_ct_ipv6_is_fragment(skb, &frag); - if (err || !frag) + if (err) { + *skb_is_ours = true; return err; + } + if (!frag) + return 0; mru = tc_skb_cb(skb)->mru; @@ -1124,6 +1135,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a, struct nf_hook_state state; int nh_ofs, err, retval; struct tcf_ct_params *p; + bool skb_is_ours = false; bool skip_add = false; bool defrag = false; struct nf_conn *ct; @@ -1160,9 +1172,18 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a, */ nh_ofs = skb_network_offset(skb); skb_pull_rcsum(skb, nh_ofs); - err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag); - if (err) + err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag, + &skb_is_ours); + if (err) { + /* The skb is still ours only when the header checks rejected + * it; returning TC_ACT_CONSUMED for such a packet would leak + * it, since no caller frees an skb it was told it no longer + * owns. + */ + if (skb_is_ours) + goto drop; goto out_frag; + } err = tcf_ct_skb_network_trim(skb, family); if (err) -- 2.53.0