From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7B6D31A4AB5 for ; Fri, 30 Aug 2024 13:07:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725023237; cv=none; b=BGkLAocfzdhCBr6CR9Nrg4+5cSFzcOXx5iGlFVDzHOXWUMn9Zsj7wHnuE4QBfVUflfC93r2f3Cfj0tU3So5HRZ/uYe5zL3Y+yIJsE9eLuGYibimt3NmOhZnei4b6gDKxo0uZmTxo2OiuM7+kFkv9I0Dm/et1zh0NGXEBQzAAm9c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725023237; c=relaxed/simple; bh=aTCt02ncGO8GcS6s0XlBKxqIsSOOxSFJqGfFRv1JVyg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; 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4sX6aC9PS0k/ZIUZSSku36VdOhx5XG5CgjDH+8/Y= Date: Fri, 30 Aug 2024 15:07:14 +0200 From: Greg Kroah-Hartman To: hsimeliere.opensource@witekio.com Cc: stable@vger.kernel.org, Eric Dumazet , Marcelo Ricardo Leitner , Willem de Bruijn , Jakub Kicinski Subject: Re: [PATCH 4.19 1/1] net: prevent mss overflow in skb_segment() Message-ID: <2024083056-subtotal-moneywise-05ab@gregkh> References: <20240830084923.27162-1-hsimeliere.opensource@witekio.com> <20240830084923.27162-2-hsimeliere.opensource@witekio.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240830084923.27162-2-hsimeliere.opensource@witekio.com> On Fri, Aug 30, 2024 at 10:44:54AM +0200, hsimeliere.opensource@witekio.com wrote: > From: Eric Dumazet > > commit 23d05d563b7e7b0314e65c8e882bc27eac2da8e7 upstream. > > Once again syzbot is able to crash the kernel in skb_segment() [1] > > GSO_BY_FRAGS is a forbidden value, but unfortunately the following > computation in skb_segment() can reach it quite easily : > > mss = mss * partial_segs; > > 65535 = 3 * 5 * 17 * 257, so many initial values of mss can lead to > a bad final result. > > Make sure to limit segmentation so that the new mss value is smaller > than GSO_BY_FRAGS. > > [1] > > general protection fault, probably for non-canonical address 0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077] > CPU: 1 PID: 5079 Comm: syz-executor993 Not tainted 6.7.0-rc4-syzkaller-00141-g1ae4cd3cbdd0 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023 > RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551 > Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00 > RSP: 0018:ffffc900043473d0 EFLAGS: 00010202 > RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597 > RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070 > RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff > R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0 > R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046 > FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > > udp6_ufo_fragment+0xa0e/0xd00 net/ipv6/udp_offload.c:109 > ipv6_gso_segment+0x534/0x17e0 net/ipv6/ip6_offload.c:120 > skb_mac_gso_segment+0x290/0x610 net/core/gso.c:53 > __skb_gso_segment+0x339/0x710 net/core/gso.c:124 > skb_gso_segment include/net/gso.h:83 [inline] > validate_xmit_skb+0x36c/0xeb0 net/core/dev.c:3626 > __dev_queue_xmit+0x6f3/0x3d60 net/core/dev.c:4338 > dev_queue_xmit include/linux/netdevice.h:3134 [inline] > packet_xmit+0x257/0x380 net/packet/af_packet.c:276 > packet_snd net/packet/af_packet.c:3087 [inline] > packet_sendmsg+0x24c6/0x5220 net/packet/af_packet.c:3119 > sock_sendmsg_nosec net/socket.c:730 [inline] > __sock_sendmsg+0xd5/0x180 net/socket.c:745 > __sys_sendto+0x255/0x340 net/socket.c:2190 > __do_sys_sendto net/socket.c:2202 [inline] > __se_sys_sendto net/socket.c:2198 [inline] > __x64_sys_sendto+0xe0/0x1b0 net/socket.c:2198 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0x40/0x110 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x63/0x6b > RIP: 0033:0x7f8692032aa9 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 d1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > RSP: 002b:00007fff8d685418 EFLAGS: 00000246 ORIG_RAX: 000000000000002c > RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8692032aa9 > RDX: 0000000000010048 RSI: 00000000200000c0 RDI: 0000000000000003 > RBP: 00000000000f4240 R08: 0000000020000540 R09: 0000000000000014 > R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff8d685480 > R13: 0000000000000001 R14: 00007fff8d685480 R15: 0000000000000003 > > Modules linked in: > ---[ end trace 0000000000000000 ]--- > RIP: 0010:skb_segment+0x181d/0x3f30 net/core/skbuff.c:4551 > Code: 83 e3 02 e9 fb ed ff ff e8 90 68 1c f9 48 8b 84 24 f8 00 00 00 48 8d 78 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e 8a 21 00 00 48 8b 84 24 f8 00 > RSP: 0018:ffffc900043473d0 EFLAGS: 00010202 > RAX: dffffc0000000000 RBX: 0000000000010046 RCX: ffffffff886b1597 > RDX: 000000000000000e RSI: ffffffff886b2520 RDI: 0000000000000070 > RBP: ffffc90004347578 R08: 0000000000000005 R09: 000000000000ffff > R10: 000000000000ffff R11: 0000000000000002 R12: ffff888063202ac0 > R13: 0000000000010000 R14: 000000000000ffff R15: 0000000000000046 > FS: 0000555556e7e380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000020010000 CR3: 0000000027ee2000 CR4: 00000000003506f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > > Fixes: 3953c46c3ac7 ("sk_buff: allow segmenting based on frag sizes") > Signed-off-by: Eric Dumazet > Cc: Marcelo Ricardo Leitner > Reviewed-by: Willem de Bruijn > Link: https://lore.kernel.org/r/20231212164621.4131800-1-edumazet@google.com > Signed-off-by: Jakub Kicinski > Signed-off-by: Greg Kroah-Hartman > Signed-off-by: Hugo SIMELIERE > --- > net/core/skbuff.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > index e03cd719b86b..cb336e79e05f 100644 > --- a/net/core/skbuff.c > +++ b/net/core/skbuff.c > @@ -3625,8 +3625,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, > /* GSO partial only requires that we trim off any excess that > * doesn't fit into an MSS sized block, so take care of that > * now. > + * Cap len to not accidentally hit GSO_BY_FRAGS. > */ > - partial_segs = len / mss; > + partial_segs = min(len, GSO_BY_FRAGS - 1U) / mss; > if (partial_segs > 1) > mss *= partial_segs; > else > -- Note, this backport causes a build warning. I'll go fix it up by hand, but next time please be more careful. thanks, greg k-h