Date: Wed, 20 Sep 2023 11:59:52 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: <syzbot+71e724675ba3958edb31@...kaller.appspotmail.com>
CC: <avagin@...il.com>, <davem@...emloft.net>, <dsahern@...nel.org>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <kuniyu@...zon.com>,
	<linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
	<pabeni@...hat.com>, <syzkaller-bugs@...glegroups.com>
Subject: Re: [syzbot] [net?] WARNING in inet_csk_get_port (2)

From: syzbot <syzbot+71e724675ba3958edb31@...kaller.appspotmail.com>
Date: Wed, 20 Sep 2023 11:02:55 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    2cf0f7156238 Merge tag 'nfs-for-6.6-2' of git://git.linux-..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=17405ab0680000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d594086f139d167
> dashboard link: https://syzkaller.appspot.com/bug?extid=71e724675ba3958edb31
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16b2e118680000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=127b55c4680000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/456b02029fa8/disk-2cf0f715.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9f9ff0c00454/vmlinux-2cf0f715.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/0ede19fba30f/bzImage-2cf0f715.xz
> 
> The issue was bisected to:
> 
> commit c48ef9c4aed3632566b57ba66cec6ec78624d4cb
> Author: Kuniyuki Iwashima <kuniyu@...zon.com>
> Date:   Mon Sep 11 18:36:57 2023 +0000
> 
>     tcp: Fix bind() regression for v4-mapped-v6 non-wildcard address.
>

We need this condition to put v4 sk and v4-mapped-v6 sk into
the same bucket.

---8<---
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index dfb1c61c0c2b..6487357d1ddd 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -822,7 +823,8 @@ static bool inet_bind2_bucket_match(const struct inet_bind2_bucket *tb,
 			return ipv6_addr_v4mapped(&tb->v6_rcv_saddr) &&
 				tb->v6_rcv_saddr.s6_addr32[3] == sk->sk_rcv_saddr;
 
-		return false;
+		return ipv6_addr_v4mapped(&sk->sk_v6_rcv_saddr) &&
+			sk->sk_v6_rcv_saddr.s6_addr32[3] == tb->rcv_saddr;
 	}
 
 	if (sk->sk_family == AF_INET6)
---8<---

Scenario is like

  1) bind(v4) creates a tb2 bucket
  2) bind(v4-mapped-v6) creates another tb2 bucket
  3) listen(v4) finds the second tb2 and trigger warning

---8<---
from socket import *

s = socket()
s.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
s.bind(('255.255.255.255', 0))

s2 = socket(AF_INET6, SOCK_STREAM)
s2.setsockopt(SOL_SOCKET, SO_REUSEPORT, 1)
s2.bind(('::ffff:255.255.255.255', s.getsockname()[1]))
s.listen()
---8<---

Will post a formal patch after doing more tests with SO_REUSEPORT.

Thanks!


> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=15567dc4680000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=17567dc4680000
> console output: https://syzkaller.appspot.com/x/log.txt?x=13567dc4680000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+71e724675ba3958edb31@...kaller.appspotmail.com
> Fixes: c48ef9c4aed3 ("tcp: Fix bind() regression for v4-mapped-v6 non-wildcard address.")
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 5049 at net/ipv4/inet_connection_sock.c:587 inet_csk_get_port+0xf96/0x2350 net/ipv4/inet_connection_sock.c:587
> Modules linked in:
> CPU: 0 PID: 5049 Comm: syz-executor288 Not tainted 6.6.0-rc2-syzkaller-00018-g2cf0f7156238 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
> RIP: 0010:inet_csk_get_port+0xf96/0x2350 net/ipv4/inet_connection_sock.c:587
> Code: 7c 24 08 e8 4c b6 8a 01 31 d2 be 88 01 00 00 48 c7 c7 e0 94 ae 8b e8 59 2e a3 f8 2e 2e 2e 31 c0 e9 04 fe ff ff e8 ca 88 d0 f8 <0f> 0b e9 0f f9 ff ff e8 be 88 d0 f8 49 8d 7e 48 e8 65 ca 5a 00 31
> RSP: 0018:ffffc90003abfbf0 EFLAGS: 00010293
> RAX: 0000000000000000 RBX: ffff888026429100 RCX: 0000000000000000
> RDX: ffff88807edcbb80 RSI: ffffffff88b73d66 RDI: ffff888026c49f38
> RBP: ffff888026c49f30 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000001 R11: 0000000000000000 R12: ffffffff9260f200
> R13: ffff888026c49880 R14: 0000000000000000 R15: ffff888026429100
> FS:  00005555557d5380(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000045ad50 CR3: 0000000025754000 CR4: 00000000003506f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  inet_csk_listen_start+0x155/0x360 net/ipv4/inet_connection_sock.c:1256
>  __inet_listen_sk+0x1b8/0x5c0 net/ipv4/af_inet.c:217
>  inet_listen+0x93/0xd0 net/ipv4/af_inet.c:239
>  __sys_listen+0x194/0x270 net/socket.c:1866
>  __do_sys_listen net/socket.c:1875 [inline]
>  __se_sys_listen net/socket.c:1873 [inline]
>  __x64_sys_listen+0x53/0x80 net/socket.c:1873
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f3a5bce3af9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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:00007ffc1a1c79e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3a5bce3af9
> RDX: 00007f3a5bce3af9 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 00007f3a5bd565f0 R08: 0000000000000006 R09: 0000000000000006
> R10: 0000000000000006 R11: 0000000000000246 R12: 0000000000000001
> R13: 431bde82d7b634db R14: 0000000000000001 R15: 0000000000000001
>  </TASK>

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