From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=91.218.175.227 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793238435; b=y2RsMOPNumIMNwZX57g5reRuOD76yb09MRSqXwSjDcDlso/3jfNOyM0M5CkpKVjrof3T QOY05bkhdbrUxlh9mNgOqqiG3GPgHdOYEHtKRiNEdbl67H9JfMcB+6VQuvgTHXxQbrP8h zJ2amkHFPZiI0YcKI4qzvWEeR7u0221fCXmBCiltSXfEwCqmyrmr8kgJ2hRlYqsTVHQRd adWRmBOuPulViIv1CiXduX2qGTKHHbSG1HPRDioqS9WtUuCfAZMiWB/F2NN9vLF7SXUSW 91zI0ArMY+y/bNg0b8GR9qUoiisdt7y4GnelGY37bupEpkm4P7QCNKmao7u2EX5S7yA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793238435; h=DMARC-Filter:X-Envelope-To:DKIM-Signature:X-Envelope-To:Received: X-Mizu-Trace-ID:X-Migadu-Flow:Message-ID:Date:MIME-Version:User-Agent: Subject:To:Cc:References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding; bh=PFzIqZjHVXD411j1Xcb58DKmChpls4qJYNm7u9vlcyc=; b=QHKnoM7ORFzMO+4tfmcojtD+g2wA6QHCMalpPNXBmnnzGp5Mg2Y3Qc5ofz7Pl13n/rtB nsmLUfjYU+yl7VNqJDskM9S5LLohCdVJpKwrRuekl2HGIKC+qSkRGxQcnexyxoMMz66UX sHmqLtv/Y6ndRAWadW0NvZylKwaqwiSi9LiTHmCKV9NPlBbWVa2nSEDNe9MvIClrxHmgw OIba8ymOEKyiPlafaQwhi9wgc+TwvFCZHWvGAc+6cp7e3k4vpVCPDoBzk/Wu1nHeRhd86 FBKVRKU27VWCHoNYoRhCzAL68Tyf5T0FEjNpQHw/OukU+lPQKcHdaTJ8T5F+vgsjidQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=vrnL24sC; arc=none smtp.remote-ip=91.218.175.227 Received: from mta0.migadu.com (out-227.mta0.migadu.com [91.218.175.227]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC7AD606A31F for ; Thu, 29 Oct 2026 01:47:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org EC7AD606A31F Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linux.dev header.i=@linux.dev header.a=rsa-sha256 header.s=key1 header.b=vrnL24sC X-Envelope-To: netdev@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=aL4JAUADBNDogSZrrKOi77qTC3m8cP+9/JJH38fu0Ds=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1793238423; v=1; x=1793843223; b=vrnL24sCvrdz5eM6eLcYpjzDHhRArkbtCiAJqlV1+p9l1dczM9szVe7E8AQIZt0ncC2ZlsCY beDZomxi3orugasFSp43DYLqYD0Hyouy2PAWASkfA+hQ22oa/hNXPxQPwyTkxTmuy0n8C6WIvxx V0nwsMrxnQghk4KhUh0zSuFw= X-Envelope-To: netdev@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 714350141f370ecb; Thu, 29 Oct 2026 01:47:03 +0000 X-Mizu-Trace-ID: 714350141f370ecb X-Migadu-Flow: FLOW_OUT Message-ID: Date: Thu, 29 Oct 2026 09:46:53 +0800 X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net v2 1/5] ipv6: restrict gc_elasticity to 31 To: Kuniyuki Iwashima Cc: netdev@vger.kernel.org, stable@vger.kernel.org, Fernando Fernandez Mancera , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Jonathan Corbet , Shuah Khan , Randy Dunlap , David Ahern , Ido Schimmel , Joel Granados , Thomas Gleixner , Petr Pavlu , Willem de Bruijn , Maoyi Xie , Jiri Wiesner , Gerd Rausch , Zhan Xusheng , Oleg Nesterov , Chia-Yu Chang , Yung Chih Su , Wyatt Feng , Hannes Frederic Sowa , Flavio Leitner , "Paul E. McKenney" , Petr Mladek , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261027104701.296240-1-jiayuan.chen@linux.dev> <20261027104701.296240-2-jiayuan.chen@linux.dev> From: Jiayuan Chen In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/29/26 7:58 AM, Kuniyuki Iwashima wrote: > On Tue, Oct 27, 2026 at 3:48 AM Jiayuan Chen wrote: >> Every counted IPv6 dst allocation runs ip6_dst_gc() once the number of >> live dst goes over gc_thresh (1024 by default). ip6_dst_gc() decays >> ip6_rt_gc_expire by gc_elasticity: the smaller gc_elasticity is, the >> smaller ip6_rt_gc_expire gets, i.e. the more aggressive the gc. >> >> ip6_dst_gc() reads ip6_rt_gc_expire into a u32, but gc_elasticity has no >> bounds at all, so writing >= 32 shifts a 32-bit value by >= 32 bits, and >> a negative value gives a negative shift count. Both are UB: >> >> val = atomic_read(&net->ipv6.ip6_rt_gc_expire); >> atomic_set(&net->ipv6.ip6_rt_gc_expire, val - (val >> rt_elasticity)); >> >> UBSAN: shift-out-of-bounds in net/ipv6/route.c:3369:53 >> shift exponent 32 is too large for 32-bit type 'unsigned int' >> CPU: 2 UID: 0 PID: 615 Comm: ping6 Not tainted 7.3.0-rc7+ #364 PREEMPT >> Call Trace: >> >> dump_stack_lvl+0xc1/0xf0 >> dump_stack+0x10/0x20 >> __ubsan_handle_shift_out_of_bounds+0x1d1/0x390 >> ip6_dst_gc.cold+0x15/0x1a >> dst_alloc+0x4e0/0x620 >> ip6_rt_cache_alloc+0x189/0x7e0 >> __ip6_rt_update_pmtu+0x68e/0x1160 >> ip6_update_pmtu+0x30c/0x3a0 >> icmpv6_err+0x1fa/0x330 >> icmpv6_notify+0x303/0x770 >> icmpv6_rcv+0xc12/0x1670 >> ip6_protocol_deliver_rcu+0xb4a/0x1520 >> ip6_input_finish+0x19c/0x400 >> ip6_input+0xd4/0x240 >> ipv6_rcv+0x1fd/0x330 >> __netif_receive_skb_one_core+0x118/0x1c0 >> __netif_receive_skb+0x21/0x150 >> process_backlog+0x37e/0x1200 >> __napi_poll.constprop.0+0xa5/0x5e0 >> net_rx_action+0x4c0/0xf70 >> handle_softirqs+0x204/0x9b0 >> __do_softirq+0x10/0x18 >> >> Make it a u8 and reject writes outside 0..31 with proc_dou8vec_minmax(). >> >> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") >> Cc: stable@vger.kernel.org >> Reviewed-by: Fernando Fernandez Mancera >> Reviewed-by: Kuniyuki Iwashima >> Signed-off-by: Jiayuan Chen >> --- >> v2: switched to u8 and proc_dou8vec_minmax(), as suggested by Kuniyuki >> Iwashima. >> --- >> include/net/netns/ipv6.h | 2 +- >> net/ipv6/route.c | 7 +++++-- >> 2 files changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h >> index ffda15318be59..aefce37c04a4f 100644 >> --- a/include/net/netns/ipv6.h >> +++ b/include/net/netns/ipv6.h >> @@ -25,11 +25,11 @@ struct netns_sysctl_ipv6 { >> int ip6_rt_gc_min_interval; >> int ip6_rt_gc_timeout; >> int ip6_rt_gc_interval; >> - int ip6_rt_gc_elasticity; >> int ip6_rt_mtu_expires; >> int ip6_rt_min_advmss; >> u32 multipath_hash_fields; >> u8 multipath_hash_policy; >> + u8 ip6_rt_gc_elasticity; >> >> __cacheline_group_begin(sysctl_ipv6_flowlabel); >> u8 flowlabel_consistency; >> diff --git a/net/ipv6/route.c b/net/ipv6/route.c >> index 94e5ef1c4f83e..abc8b811cd423 100644 >> --- a/net/ipv6/route.c >> +++ b/net/ipv6/route.c >> @@ -6579,6 +6579,8 @@ static int ipv6_sysctl_rtcache_flush(const struct ctl_table *ctl, int write, >> return 0; >> } >> >> +static int ip6_rt_gc_elasticity_max = 31; > as you need v3, s/int/u8/ > Hi Kuniyuki, proc_dou8vec_minmax() put extra1/extra2 into proc_uint_conv(), which reads them as unsigned int, so the max has to stay an int like tcp_syn_retries_max and friends; a u8 there would read three bytes past the variable.