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From:   Kuniyuki Iwashima <kuniyu@amazon.com>
To:     <syzbot+444ca0907e96f7c5e48b@syzkaller.appspotmail.com>
CC:     <bpf@vger.kernel.org>, <davem@davemloft.net>, <dsahern@kernel.org>,
        <edumazet@google.com>, <kuba@kernel.org>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <pabeni@redhat.com>, <syzkaller-bugs@googlegroups.com>,
        <willemdebruijn.kernel@gmail.com>, <kuniyu@amazon.com>
Subject: Re: [syzbot] [net?] general protection fault in __sk_mem_raise_allocated
Date:   Mon, 22 May 2023 10:32:00 -0700
Message-ID: <20230522173200.59608-1-kuniyu@amazon.com>
In-Reply-To: <000000000000182b5f05fc41db4a@google.com>
References: <000000000000182b5f05fc41db4a@google.com>
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From: syzbot <syzbot+444ca0907e96f7c5e48b@syzkaller.appspotmail.com>
Date: Sun, 21 May 2023 22:51:02 -0700
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    f1fcbaa18b28 Linux 6.4-rc2
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1216efba280000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ac0db1213414a978
> dashboard link: https://syzkaller.appspot.com/bug?extid=444ca0907e96f7c5e48b
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ea7e2a44b1f9/disk-f1fcbaa1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/f4e3201419a9/vmlinux-f1fcbaa1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c2cd3eb9954b/bzImage-f1fcbaa1.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+444ca0907e96f7c5e48b@syzkaller.appspotmail.com
> 
> general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
> CPU: 0 PID: 6829 Comm: syz-executor.1 Not tainted 6.4.0-rc2-syzkaller #0

The last syz-executor.1 seems to create UDP_LITE (0x88) sk.

https://syzkaller.appspot.com/text?tag=CrashLog&x=1216efba280000

---8<---
14:25:52 executing program 1:
r0 = socket$inet6(0xa, 0x80002, 0x88)
bind$inet6(r0, &(0x7f00000001c0)={0xa, 0x10010000004e20}, 0x1c)
syz_emit_ethernet(0x83, &(0x7f0000000040)=ANY=[@ANYBLOB="aaaaaaaaaaaaaaaaaaab90aa86dd601bfc97004d8880fe800001000000000000000000000600ff02000000000000000000000000000101004e20004590"], 0x0)
ppoll(&(0x7f0000000240)=[{r0}], 0x1, &(0x7f0000000140), 0x0, 0x0)
---8<---

udplitev6_rcv() calls __udp6_lib_rcv(), which expects .sysctl_rmem_offset
or sysctl_rmem is configured in sk_prot, but udplitev6_prot has neither.

I'll post a fix after testing.

Thanks,
Kuniyuki


> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
> RIP: 0010:sk_get_rmem0 include/net/sock.h:2907 [inline]
> RIP: 0010:__sk_mem_raise_allocated+0x806/0x17a0 net/core/sock.c:3006
> Code: c1 ea 03 80 3c 02 00 0f 85 23 0f 00 00 48 8b 44 24 08 48 8b 98 38 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <0f> b6 14 02 48 89 d8 83 e0 07 83 c0 03 38 d0 0f 8d 6f 0a 00 00 8b
> RSP: 0018:ffffc90005d7f450 EFLAGS: 00010246
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90004d92000
> RDX: 0000000000000000 RSI: ffffffff88066482 RDI: ffffffff8e2ccbb8
> RBP: ffff8880173f7000 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000030000
> R13: 0000000000000001 R14: 0000000000000340 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff8880b9800000(0063) knlGS:00000000f7f1cb40
> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> CR2: 000000002e82f000 CR3: 0000000034ff0000 CR4: 00000000003506f0
> Call Trace:
>  <TASK>
>  __sk_mem_schedule+0x6c/0xe0 net/core/sock.c:3077
>  udp_rmem_schedule net/ipv4/udp.c:1539 [inline]
>  __udp_enqueue_schedule_skb+0x776/0xb30 net/ipv4/udp.c:1581
>  __udpv6_queue_rcv_skb net/ipv6/udp.c:666 [inline]
>  udpv6_queue_rcv_one_skb+0xc39/0x16c0 net/ipv6/udp.c:775
>  udpv6_queue_rcv_skb+0x194/0xa10 net/ipv6/udp.c:793
>  __udp6_lib_mcast_deliver net/ipv6/udp.c:906 [inline]
>  __udp6_lib_rcv+0x1bda/0x2bd0 net/ipv6/udp.c:1013
>  ip6_protocol_deliver_rcu+0x2e7/0x1250 net/ipv6/ip6_input.c:437
>  ip6_input_finish+0x150/0x2f0 net/ipv6/ip6_input.c:482
>  NF_HOOK include/linux/netfilter.h:303 [inline]
>  NF_HOOK include/linux/netfilter.h:297 [inline]
>  ip6_input+0xa0/0xd0 net/ipv6/ip6_input.c:491
>  ip6_mc_input+0x40b/0xf50 net/ipv6/ip6_input.c:585
>  dst_input include/net/dst.h:468 [inline]
>  ip6_rcv_finish net/ipv6/ip6_input.c:79 [inline]
>  NF_HOOK include/linux/netfilter.h:303 [inline]
>  NF_HOOK include/linux/netfilter.h:297 [inline]
>  ipv6_rcv+0x250/0x380 net/ipv6/ip6_input.c:309
>  __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5491
>  __netif_receive_skb+0x1f/0x1c0 net/core/dev.c:5605
>  netif_receive_skb_internal net/core/dev.c:5691 [inline]
>  netif_receive_skb+0x133/0x7a0 net/core/dev.c:5750
>  tun_rx_batched+0x4b3/0x7a0 drivers/net/tun.c:1553
>  tun_get_user+0x2452/0x39c0 drivers/net/tun.c:1989
>  tun_chr_write_iter+0xdf/0x200 drivers/net/tun.c:2035
>  call_write_iter include/linux/fs.h:1868 [inline]
>  new_sync_write fs/read_write.c:491 [inline]
>  vfs_write+0x945/0xd50 fs/read_write.c:584
>  ksys_write+0x12b/0x250 fs/read_write.c:637
>  do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
>  __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
>  do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203
>  entry_SYSENTER_compat_after_hwframe+0x70/0x82
> RIP: 0023:0xf7f21579
> Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
> RSP: 002b:00000000f7f1c590 EFLAGS: 00000282 ORIG_RAX: 0000000000000004
> RAX: ffffffffffffffda RBX: 00000000000000c8 RCX: 0000000020000040
> RDX: 0000000000000083 RSI: 00000000f734e000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:sk_get_rmem0 include/net/sock.h:2907 [inline]
> RIP: 0010:__sk_mem_raise_allocated+0x806/0x17a0 net/core/sock.c:3006
> Code: c1 ea 03 80 3c 02 00 0f 85 23 0f 00 00 48 8b 44 24 08 48 8b 98 38 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <0f> b6 14 02 48 89 d8 83 e0 07 83 c0 03 38 d0 0f 8d 6f 0a 00 00 8b
> RSP: 0018:ffffc90005d7f450 EFLAGS: 00010246
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffc90004d92000
> RDX: 0000000000000000 RSI: ffffffff88066482 RDI: ffffffff8e2ccbb8
> RBP: ffff8880173f7000 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000030000
> R13: 0000000000000001 R14: 0000000000000340 R15: 0000000000000001
> FS:  0000000000000000(0000) GS:ffff8880b9800000(0063) knlGS:00000000f7f1cb40
> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
> CR2: 000000002e82f000 CR3: 0000000034ff0000 CR4: 00000000003506f0
> ----------------
> Code disassembly (best guess):
>    0:	c1 ea 03             	shr    $0x3,%edx
>    3:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1)
>    7:	0f 85 23 0f 00 00    	jne    0xf30
>    d:	48 8b 44 24 08       	mov    0x8(%rsp),%rax
>   12:	48 8b 98 38 01 00 00 	mov    0x138(%rax),%rbx
>   19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>   20:	fc ff df
>   23:	48 89 da             	mov    %rbx,%rdx
>   26:	48 c1 ea 03          	shr    $0x3,%rdx
> * 2a:	0f b6 14 02          	movzbl (%rdx,%rax,1),%edx <-- trapping instruction
>   2e:	48 89 d8             	mov    %rbx,%rax
>   31:	83 e0 07             	and    $0x7,%eax
>   34:	83 c0 03             	add    $0x3,%eax
>   37:	38 d0                	cmp    %dl,%al
>   39:	0f 8d 6f 0a 00 00    	jge    0xaae
>   3f:	8b                   	.byte 0x8b
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
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> 
> syzbot will keep track of this issue. See:
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> 
> If the bug is already fixed, let syzbot know by replying with:
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> 
> If you want to change bug's subsystems, reply with:
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> (See the list of subsystem names on the web dashboard)
> 
> If the bug is a duplicate of another bug, reply with:
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> 
> If you want to undo deduplication, reply with:
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