[syzbot] BUG: unable to handle kernel NULL pointer dereference in __tcp_transmit_skb

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 36c2e31ad25b net: geneve: add missing netlink policy and s..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17c308a5700000
kernel config: https://syzkaller.appspot.com/x/.config?x=4a15e2288cf165c9
dashboard link: https://syzkaller.appspot.com/bug?extid=090d23ddbd5cd185c2e0
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171eadbd700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cacda3700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+090d23...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 13fd5067 P4D 13fd5067 PUD 77ebc067 PMD 0
Oops: 0010 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 7423 Comm: syz-executor720 Not tainted 5.17.0-rc8-syzkaller-02803-g36c2e31ad25b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900001d0a60 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88801e00cd10 RCX: 0000000000000100
RDX: 1ffff11003c019a3 RSI: ffff8880155c5c80 RDI: ffff888014bac800
RBP: ffff888014bac800 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff87bccdc7 R11: 0000000000000000 R12: ffff8880155c5c80
R13: 0000000000000000 R14: ffff888014bacf60 R15: ffff88807527012c
FS: 000055555733b3c0(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000757b0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
__tcp_transmit_skb+0x1098/0x38b0 net/ipv4/tcp_output.c:1371
tcp_transmit_skb net/ipv4/tcp_output.c:1420 [inline]
tcp_xmit_probe_skb+0x28c/0x320 net/ipv4/tcp_output.c:4006
tcp_write_wakeup+0x1bd/0x610 net/ipv4/tcp_output.c:4059
tcp_send_probe0+0x44/0x560 net/ipv4/tcp_output.c:4074
tcp_probe_timer net/ipv4/tcp_timer.c:398 [inline]
tcp_write_timer_handler+0x9ed/0xbc0 net/ipv4/tcp_timer.c:626
tcp_write_timer+0xa2/0x2b0 net/ipv4/tcp_timer.c:642
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1421
expire_timers kernel/time/timer.c:1466 [inline]
__run_timers.part.0+0x67c/0xa30 kernel/time/timer.c:1734
__run_timers kernel/time/timer.c:1715 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1747
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
invoke_softirq kernel/softirq.c:432 [inline]
__irq_exit_rcu+0x123/0x180 kernel/softirq.c:637
irq_exit_rcu+0x5/0x20 kernel/softirq.c:649
sysvec_apic_timer_interrupt+0x93/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:lock_acquire+0x1ef/0x510 kernel/locking/lockdep.c:5607
Code: e4 a4 7e 83 f8 01 0f 85 b4 02 00 00 9c 58 f6 c4 02 0f 85 9f 02 00 00 48 83 7c 24 08 00 74 01 fb 48 b8 00 00 00 00 00 fc ff df <48> 01 c3 48 c7 03 00 00 00 00 48 c7 43 08 00 00 00 00 48 8b 84 24
RSP: 0018:ffffc90002eaf888 EFLAGS: 00000206
RAX: dffffc0000000000 RBX: 1ffff920005d5f13 RCX: 5ad5b746ce328923
RDX: 1ffff1100e5374eb RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: ffffffff8fe0c947
R10: fffffbfff1fc1928 R11: 0000000000000001 R12: 0000000000000002
R13: 0000000000000000 R14: ffffffff8bb84ca0 R15: 0000000000000000
rcu_lock_acquire include/linux/rcupdate.h:268 [inline]
rcu_read_lock include/linux/rcupdate.h:694 [inline]
fib_lookup.constprop.0+0x8f/0x460 include/net/ip_fib.h:377
ip_route_output_key_hash_rcu+0xf54/0x2c80 net/ipv4/route.c:2737
ip_route_output_key_hash+0x183/0x2f0 net/ipv4/route.c:2627
__ip_route_output_key include/net/route.h:127 [inline]
ip_route_output_flow+0x23/0x150 net/ipv4/route.c:2857
ip_route_newports include/net/route.h:343 [inline]
tcp_v4_connect+0x12a5/0x1d00 net/ipv4/tcp_ipv4.c:283
__inet_stream_connect+0x8cf/0xed0 net/ipv4/af_inet.c:660
inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:724
smc_connect+0x230/0x450 net/smc/af_smc.c:1522
__sys_connect_file+0x155/0x1a0 net/socket.c:1900
__sys_connect+0x161/0x190 net/socket.c:1917
__do_sys_connect net/socket.c:1927 [inline]
__se_sys_connect net/socket.c:1924 [inline]
__x64_sys_connect+0x6f/0xb0 net/socket.c:1924
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f23b4ec0889
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 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 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffce8f74658 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007ffce8f746b0 RCX: 00007f23b4ec0889
RDX: 0000000000000010 RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 000000000000cf1c R09: 000000000000cf1c
R10: 0000000000000004 R11: 0000000000000246 R12: 00007ffce8f746a0
R13: 000000000000cf1c R14: 00007ffce8f7469c R15: 431bde82d7b634db
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffffc900001d0a60 EFLAGS: 00010246
RAX: dffffc0000000000 RBX: ffff88801e00cd10 RCX: 0000000000000100
RDX: 1ffff11003c019a3 RSI: ffff8880155c5c80 RDI: ffff888014bac800
RBP: ffff888014bac800 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff87bccdc7 R11: 0000000000000000 R12: ffff8880155c5c80
R13: 0000000000000000 R14: ffff888014bacf60 R15: ffff88807527012c
FS: 000055555733b3c0(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 00000000757b0000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: e4 a4 in $0xa4,%al
2: 7e 83 jle 0xffffff87
4: f8 clc
5: 01 0f add %ecx,(%rdi)
7: 85 b4 02 00 00 9c 58 test %esi,0x589c0000(%rdx,%rax,1)
e: f6 c4 02 test $0x2,%ah
11: 0f 85 9f 02 00 00 jne 0x2b6
17: 48 83 7c 24 08 00 cmpq $0x0,0x8(%rsp)
1d: 74 01 je 0x20
1f: fb sti
20: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
27: fc ff df
* 2a: 48 01 c3 add %rax,%rbx <-- trapping instruction
2d: 48 c7 03 00 00 00 00 movq $0x0,(%rbx)
34: 48 c7 43 08 00 00 00 movq $0x0,0x8(%rbx)
3b: 00
3c: 48 rex.W
3d: 8b .byte 0x8b
3e: 84 .byte 0x84
3f: 24 .byte 0x24


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Eric Dumazet]

On Wed, Mar 23, 2022 at 5:13 PM syzbot
<syzbot+090d23...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 36c2e31ad25b net: geneve: add missing netlink policy and s..
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17c308a5700000
> kernel config: https://syzkaller.appspot.com/x/.config?x=4a15e2288cf165c9
> dashboard link: https://syzkaller.appspot.com/bug?extid=090d23ddbd5cd185c2e0
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171eadbd700000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cacda3700000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+090d23...@syzkaller.appspotmail.com
>

AF_SMC does not handle TCP_REPAIR properly.

Look at commit d9e4c129181004e ("mptcp: only admit explicitly
supported sockopt") for an equivalent bug/fix.

[syzbot]

syzbot has bisected this issue to:

commit f2f2325ec79970807012dfc9e716cdbb02d9b574
Author: Eric Dumazet <edum...@google.com>
Date: Fri Feb 4 20:15:46 2022 +0000

ip6mr: ip6mr_sk_done() can exit early in common cases

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16299d7b700000
start commit: 36c2e31ad25b net: geneve: add missing netlink policy and s..
git tree: net-next
final oops: https://syzkaller.appspot.com/x/report.txt?x=15299d7b700000
console output: https://syzkaller.appspot.com/x/log.txt?x=11299d7b700000

kernel config: https://syzkaller.appspot.com/x/.config?x=4a15e2288cf165c9
dashboard link: https://syzkaller.appspot.com/bug?extid=090d23ddbd5cd185c2e0

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171eadbd700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cacda3700000

Reported-by: syzbot+090d23...@syzkaller.appspotmail.com
Fixes: f2f2325ec799 ("ip6mr: ip6mr_sk_done() can exit early in common cases")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

[Karsten Graul]

On 24/03/2022 02:41, Eric Dumazet wrote:
> On Wed, Mar 23, 2022 at 5:13 PM syzbot
> <syzbot+090d23...@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit: 36c2e31ad25b net: geneve: add missing netlink policy and s..
>> git tree: net-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=17c308a5700000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=4a15e2288cf165c9
>> dashboard link: https://syzkaller.appspot.com/bug?extid=090d23ddbd5cd185c2e0
>> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=171eadbd700000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12cacda3700000
>>
>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>> Reported-by: syzbot+090d23...@syzkaller.appspotmail.com
>>
>
> AF_SMC does not handle TCP_REPAIR properly.
>
> Look at commit d9e4c129181004e ("mptcp: only admit explicitly
> supported sockopt") for an equivalent bug/fix.

Got it, we will fix that.

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.