From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794427247; b=vzy4St+BLmPwpKAlsnLSrnada8g/OpT0dxz3mLPXBNnkhp0PudH64zvDS0Ppyokt6E/A EGTF9Eg7iksBIlJdUUv2S5NI5G5hDGLsaC31ztkzOvDoPf1d2lV0svGc/umSQ7LnX2KyD JmMHSyt8kSA+e2fwk9VKR2SEVsm1cJZYu5NoZ8E2m0SypYAn4J+O4DAUFIEHdVOhtgp2o K/ZdVs8yzBwVIkATQo4Rw/4R7aJmHMnqvQMo/5xP0l2K84fA5LRWN9WXb2raRVxsxMX1l LLDNdFmb/nHRlDLCzKmY4T63I7hFFmyQe24nPl2aQ39ri4A+zvDG++VHt3+V3a0U3Ag== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794427247; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=UaefB8A3yTLegoLwLnY17kIeCgiwMftxOiYmoejib2c=; b=Uhwm1SgJEBR2VuCiSw7+gAsMdLpYCeqKF/OALOIh2lFEgiORRatLUKIxz+ak9EmXak4e EREgxrH5Icf075vuWJcg6xE0ntk7p+8sRto0K7nSKn6VjzjDlH4bnUgYkv1pOluv9fflW 0ZNYZNGMLc7No7ANBl21mB2Yf0cDw/8yxirZ2ZBtuCwMtFjQU1f+a2X0PE+NGXYI+pmTV hlbaA+NUteE8XI1Royq3pzhCl7sPNLVacGiWmjQ3taIM1N2exAqd8zswyWeJ6BBWnbavg xloWwZIzK3n6UXqHwP4nwVIbEFN7a1nlK3JkiLfVJjZWJST4z2n7iiYEqNh3nddbZXg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dtCdaC6h; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CD157606A31C for ; Wed, 11 Nov 2026 20:00:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=dtCdaC6h Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C9C61F00A05; Wed, 11 Nov 2026 20:00:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794427247; bh=UaefB8A3yTLegoLwLnY17kIeCgiwMftxOiYmoejib2c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dtCdaC6h4OM8lxmJ/GN/aBb9Ank2XXIrsaGJc7Qvzlx1Ck4JrzriptyLu38xmBF5s 5d6FlJHGsdmgczpHFGLUU7HPifZZTOSwlysJBQFcS9wM/jBLtyT567JhA/8EGadWmx 5ch3VaDA4lJFdxl9UZEepBt/RIzFUeSOp0WA1Ch1UbS8YVJ2xdhuvr8brgGHcWGiRa JmlZQiMWO6moaJbRLIptI427sPukCTBFNj8YEssLPLq1Sbora87TKwxW0Fwaolcn9Y UC/aerD+Wtj/CtuF154T429UegRX36vO7qAetfGWfjDyGCXzddErkB5RX17SmDEaVR GA8iAL20+28HA== From: Sasha Levin To: stable@vger.kernel.org Cc: Eric Dumazet , Kyle Zeng , Florian Westphal , Ido Schimmel , Jiayuan Chen , Wang Zhan , Paolo Abeni , Sasha Levin Subject: [PATCH 6.6.y] inet: frags: limit the truesize of a reassembly queue Date: Wed, 11 Nov 2026 15:00:45 -0500 Message-ID: <20261111200025.4039824-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261109201201-failed-6.6-3ae20e4697eb@kernel.org> References: <20261109201201-failed-6.6-3ae20e4697eb@kernel.org> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Eric Dumazet [ Upstream commit 3ae20e4697eb969104fe4b1e98a675f0100382b6 ] The truesize of fragments in a reassembly queue is only bounded by the per netns ipfrag_high_thresh sysctl, which has no upper limit. inet_frag_reasm_finish() sums the truesize of all fragments in an int. If this sum reaches 2^32, it wraps, and the final sk_wmem_alloc adjustment of the socket owning the reassembled skb can cancel its own reference, leading to a use-after-free of this socket. This can be triggered from an unprivileged user/network namespace, raising ipfrag_high_thresh and using padded TUN packets, which keep a large truesize after being trimmed by ip_rcv_core(). Track the sum of the truesize of fragments in each queue, and refuse a fragment that would make it bigger than INT_MAX / 2. Callers kill the queue on this error. This bound is far above the needs of legitimate traffic. Fixes: 18685451fc4e ("inet: inet_defrag: prevent sk release while still in use") Cc: stable@vger.kernel.org Reported-by: Kyle Zeng Cc: Florian Westphal Signed-off-by: Eric Dumazet Reviewed-by: Ido Schimmel Reviewed-by: Jiayuan Chen Tested-by: Wang Zhan Link: https://patch.msgid.link/20261030081225.2575462-1-edumazet@kernel.org Signed-off-by: Paolo Abeni [ sashal: adjusted context for missing security-path checks and nf_reset_ct() in inet_frag_queue_insert() ] Signed-off-by: Sasha Levin --- include/net/inet_frag.h | 9 +++++++++ net/ipv4/inet_fragment.c | 5 +++++ 2 files changed, 14 insertions(+) diff --git a/include/net/inet_frag.h b/include/net/inet_frag.h index 365925c9d2628..6aea2d1ac376f 100644 --- a/include/net/inet_frag.h +++ b/include/net/inet_frag.h @@ -79,6 +79,7 @@ struct frag_v6_compare_key { * @tstamp_type: stamp has a mono delivery time (EDT) * @flags: fragment queue flags * @max_size: maximum received fragment size + * @truesize: sum of the truesize of queued fragments * @fqdir: pointer to struct fqdir * @rcu: rcu head for freeing deferall */ @@ -100,6 +101,7 @@ struct inet_frag_queue { u8 tstamp_type; __u8 flags; u16 max_size; + unsigned int truesize; struct fqdir *fqdir; struct rcu_head rcu; }; @@ -171,6 +173,13 @@ extern const u8 ip_frag_ecn_table[16]; #define IPFRAG_OK 0 #define IPFRAG_DUP 1 #define IPFRAG_OVERLAP 2 +#define IPFRAG_TOOBIG 4 + +/* Max sum of the truesize of fragments in a queue. This keeps the sums + * done in inet_frag_reasm_prepare() and inet_frag_reasm_finish() well + * below INT_MAX. Legitimate traffic stays far below this limit. + */ +#define INET_FRAG_MAX_TRUESIZE (INT_MAX / 2) int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, int offset, int end); void *inet_frag_reasm_prepare(struct inet_frag_queue *q, struct sk_buff *skb, diff --git a/net/ipv4/inet_fragment.c b/net/ipv4/inet_fragment.c index 90709f2fdab88..c7be3060698ba 100644 --- a/net/ipv4/inet_fragment.c +++ b/net/ipv4/inet_fragment.c @@ -337,6 +337,7 @@ void inet_frag_queue_flush(struct inet_frag_queue *q, q->rb_fragments = RB_ROOT; q->fragments_tail = NULL; q->last_run_head = NULL; + q->truesize = 0; } EXPORT_SYMBOL(inet_frag_queue_flush); @@ -441,6 +442,9 @@ int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, { struct sk_buff *last = q->fragments_tail; + if (skb->truesize > INET_FRAG_MAX_TRUESIZE - q->truesize) + return IPFRAG_TOOBIG; + /* An IP fragment is never a GSO packet, but an untrusted source * (virtio_net_hdr) may have attached GSO metadata to it. Do not let * that reach the reassembled skb, whose head keeps the first @@ -503,6 +507,7 @@ int inet_frag_queue_insert(struct inet_frag_queue *q, struct sk_buff *skb, FRAG_CB(skb)->ip_defrag_offset = offset; + q->truesize += skb->truesize; return IPFRAG_OK; } EXPORT_SYMBOL(inet_frag_queue_insert); -- 2.53.0