BUG: unable to handle kernel paging request in ip6_pol_route

[Wei Chen]

Dear Linux Developer,

Recently when using our tool to fuzz kernel, the following crash was triggered.

HEAD commit: d418a331631b v6.1.0-rc5
git tree: kmsan
compiler: gcc 8.4.0
console output:
https://drive.google.com/file/d/1mvry1KoOmIUFrTN-qWTkHS9W0w7fRJvb/view?usp=share_link
kernel config: https://drive.google.com/file/d/1qltDw7jrn7_DnXvhf7MgsxO08nqGSCDe/view?usp=share_link

Unfortunately, I didn't have a reproducer for this bug.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: Wei Chen <harperchen1110@xxxxxxxxx>

BUG: unable to handle page fault for address: ffff887f0c83f180
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 14 Comm: ksoftirqd/0 Not tainted 6.1.0-rc5-63183-gd418a331631b #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
Ubuntu-1.8.2-1ubuntu1 04/01/2014
RIP: 0010:rt6_get_pcpu_route net/ipv6/route.c:1396 [inline]
RIP: 0010:ip6_pol_route+0x465/0x690 net/ipv6/route.c:2251
Code: 84 24 60 07 00 00 48 89 45 a8 e9 c2 fc ff ff e8 f1 30 4b fd 48
8d 75 a8 4c 89 e7 e8 25 8b ff ff e9 c4 fc ff ff e8 db 30 4b fd <44> 8b
bb 80 00 00 00 31 ff 44 89 fe e8 da 31 4b fd 45 85 ff 74 8a
RSP: 0018:ffff88800705f988 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff887f0c83f100 RCX: ffff8880070b0000
RDX: 0000000000000000 RSI: ffff8880070b0000 RDI: 0000000000000002
RBP: ffff88800705fa08 R08: ffffffff83e034d5 R09: 0000000000000000
R10: 0000000000000007 R11: ffff887f0c83f100 R12: ffff88800db93480
R13: 0000607f810261e0 R14: 0000000000000080 R15: 0000000000000019
FS:  0000000000000000(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff887f0c83f180 CR3: 000000000e17a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ip6_pol_route_input+0x38/0x50 net/ipv6/route.c:2275
 pol_lookup_func include/net/ip6_fib.h:582 [inline]
 fib6_rule_lookup+0x6c/0x330 net/ipv6/fib6_rules.c:116
 ip6_route_input_lookup+0x8f/0xa0 net/ipv6/route.c:2287
 ip6_route_input+0x260/0x350 net/ipv6/route.c:2583
 ip6_rcv_finish_core.isra.21+0x6c/0x180 net/ipv6/ip6_input.c:66
 ip6_rcv_finish+0xad/0xf0 net/ipv6/ip6_input.c:77
 NF_HOOK include/linux/netfilter.h:302 [inline]
 NF_HOOK include/linux/netfilter.h:296 [inline]
 ipv6_rcv+0x10d/0x120 net/ipv6/ip6_input.c:309
 __netif_receive_skb_one_core+0x69/0xa0 net/core/dev.c:5489
 __netif_receive_skb+0x22/0xa0 net/core/dev.c:5603
 process_backlog+0xda/0x1b0 net/core/dev.c:5931
 __napi_poll+0x44/0x2c0 net/core/dev.c:6498
 napi_poll net/core/dev.c:6565 [inline]
 net_rx_action+0x397/0x480 net/core/dev.c:6676
 __do_softirq+0xe4/0x2d7 kernel/softirq.c:571
 run_ksoftirqd kernel/softirq.c:934 [inline]
 run_ksoftirqd+0x26/0x30 kernel/softirq.c:926
 smpboot_thread_fn+0x27a/0x370 kernel/smpboot.c:164
 kthread+0x13e/0x180 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>
Modules linked in:
CR2: ffff887f0c83f180
---[ end trace 0000000000000000 ]---
RIP: 0010:rt6_get_pcpu_route net/ipv6/route.c:1396 [inline]
RIP: 0010:ip6_pol_route+0x465/0x690 net/ipv6/route.c:2251
Code: 84 24 60 07 00 00 48 89 45 a8 e9 c2 fc ff ff e8 f1 30 4b fd 48
8d 75 a8 4c 89 e7 e8 25 8b ff ff e9 c4 fc ff ff e8 db 30 4b fd <44> 8b
bb 80 00 00 00 31 ff 44 89 fe e8 da 31 4b fd 45 85 ff 74 8a
RSP: 0018:ffff88800705f988 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff887f0c83f100 RCX: ffff8880070b0000
RDX: 0000000000000000 RSI: ffff8880070b0000 RDI: 0000000000000002
RBP: ffff88800705fa08 R08: ffffffff83e034d5 R09: 0000000000000000
R10: 0000000000000007 R11: ffff887f0c83f100 R12: ffff88800db93480
R13: 0000607f810261e0 R14: 0000000000000080 R15: 0000000000000019
FS:  0000000000000000(0000) GS:ffff88803ec00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff887f0c83f180 CR3: 000000000e17a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess), 4 bytes skipped:
   0: 00 00                add    %al,(%rax)
   2: 48 89 45 a8          mov    %rax,-0x58(%rbp)
   6: e9 c2 fc ff ff        jmpq   0xfffffccd
   b: e8 f1 30 4b fd        callq  0xfd4b3101
  10: 48 8d 75 a8          lea    -0x58(%rbp),%rsi
  14: 4c 89 e7              mov    %r12,%rdi
  17: e8 25 8b ff ff        callq  0xffff8b41
  1c: e9 c4 fc ff ff        jmpq   0xfffffce5
  21: e8 db 30 4b fd        callq  0xfd4b3101
* 26: 44 8b bb 80 00 00 00 mov    0x80(%rbx),%r15d <-- trapping instruction
  2d: 31 ff                xor    %edi,%edi
  2f: 44 89 fe              mov    %r15d,%esi
  32: e8 da 31 4b fd        callq  0xfd4b3211
  37: 45 85 ff              test   %r15d,%r15d
  3a: 74 8a                je     0xffffffc6

Best,
Wei