BUG: unable to handle kernel NULL pointer dereference in sctp_sched_dequeue_common

[Wei Chen]

Dear Linux Developer,

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

HEAD commit:  c5eb0a61238d Linux 5.18-rc6
git tree: upstream
compiler: clang 12.0.0
console output:
https://drive.google.com/file/d/1zbd9t-NNorzTXESdQ3bxE-q9uLu-Bm9d/view?usp=sharing
Syzlang reproducer:
https://drive.google.com/file/d/18wnwTf53Ln4K8e4G9d8hS4-e0URQKHet/view?usp=sharing
C reproducer: https://drive.google.com/file/d/1ttiMq0WYi46zFP1II8O9eee_dvDweIb6/view?usp=sharing
kernel config: https://drive.google.com/file/d/1fITkvcuglspvuhI0mhXUndx112fJmcOZ/view?usp=sharing

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

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 12f83067 P4D 12f83067 PUD 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 5.18.0-rc6 #12
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:__list_del_entry_valid+0x26/0x80
Code: 00 00 00 00 55 48 89 e5 48 89 fe 48 ba 00 01 00 00 00 00 ad de
48 8b 0f 48 39 d1 74 22 48 8b 46 08 48 83 c2 22 48 39 d0 74 25 <48> 8b
10 48 39 f2 75 2d 48 8b 51 08 48 39 f2 75 37 b0 01 5d c3 48
RSP: 0018:ffff888007313720 EFLAGS: 00010217
RAX: 0000000000000000 RBX: ffff88800c6283e8 RCX: 0000000000000000
RDX: dead000000000122 RSI: ffff88800c6283e8 RDI: ffff88800c6283e8
RBP: ffff888007313720 R08: ffffffff84399732 R09: ffffffff84392a74
R10: 0000000000000042 R11: ffff8880072a2f80 R12: ffff8880138be238
R13: ffff888016cdb000 R14: ffff888016cdb5a0 R15: ffff888016cdb000
FS:  0000000000000000(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000012f82000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 sctp_sched_dequeue_common+0x1c/0x90
 sctp_sched_prio_dequeue+0x67/0x80
 __sctp_outq_teardown+0x299/0x380
 sctp_outq_free+0x15/0x20
 sctp_association_free+0xc3/0x440
 sctp_do_sm+0x1ca7/0x2210
 sctp_assoc_bh_rcv+0x1f6/0x340
 sctp_inq_push+0x98/0xb0
 sctp_rcv+0x134e/0x16b0
 sctp6_rcv+0x1b/0x30
 ip6_protocol_deliver_rcu+0x5b7/0x930
 ip6_input+0x80/0x140
 ip6_rcv_finish+0x16e/0x1d0
 ipv6_rcv+0x72/0x110
 __netif_receive_skb+0x66/0x140
 process_backlog+0x13d/0x230
 __napi_poll+0x4b/0x310
 net_rx_action+0x1ae/0x410
 __do_softirq+0x16e/0x30f
 run_ksoftirqd+0x23/0x30
 smpboot_thread_fn+0x210/0x370
 kthread+0x124/0x160
 ret_from_fork+0x1f/0x30
 </TASK>
Modules linked in:
Dumping ftrace buffer:
   (ftrace buffer empty)
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:__list_del_entry_valid+0x26/0x80
Code: 00 00 00 00 55 48 89 e5 48 89 fe 48 ba 00 01 00 00 00 00 ad de
48 8b 0f 48 39 d1 74 22 48 8b 46 08 48 83 c2 22 48 39 d0 74 25 <48> 8b
10 48 39 f2 75 2d 48 8b 51 08 48 39 f2 75 37 b0 01 5d c3 48
RSP: 0018:ffff888007313720 EFLAGS: 00010217
RAX: 0000000000000000 RBX: ffff88800c6283e8 RCX: 0000000000000000
RDX: dead000000000122 RSI: ffff88800c6283e8 RDI: ffff88800c6283e8
RBP: ffff888007313720 R08: ffffffff84399732 R09: ffffffff84392a74
R10: 0000000000000042 R11: ffff8880072a2f80 R12: ffff8880138be238
R13: ffff888016cdb000 R14: ffff888016cdb5a0 R15: ffff888016cdb000
FS:  0000000000000000(0000) GS:ffff88807dc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000012f82000 CR4: 0000000000750ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
----------------
Code disassembly (best guess):
   0: 00 00                          add    %al,(%rax)
   2: 00 00                          add    %al,(%rax)
   4: 55                               push   %rbp
   5: 48 89 e5                     mov    %rsp,%rbp
   8: 48 89 fe                      mov    %rdi,%rsi
   b: 48 ba 00 01 00 00 00 movabs $0xdead000000000100,%rdx
  12: 00 ad de
  15: 48 8b 0f                     mov    (%rdi),%rcx
  18: 48 39 d1                    cmp    %rdx,%rcx
  1b: 74 22                         je     0x3f
  1d: 48 8b 46 08               mov    0x8(%rsi),%rax
  21: 48 83 c2 22               add    $0x22,%rdx
  25: 48 39 d0                    cmp    %rdx,%rax
  28: 74 25                         je     0x4f
* 2a: 48 8b 10                   mov    (%rax),%rdx <-- trapping instruction
  2d: 48 39 f2                    cmp    %rsi,%rdx
  30: 75 2d                        jne    0x5f
  32: 48 8b 51 08              mov    0x8(%rcx),%rdx
  36: 48 39 f2                    cmp    %rsi,%rdx
  39: 75 37                        jne    0x72
  3b: b0 01                        mov    $0x1,%al
  3d: 5d                             pop    %rbp
  3e: c3                             retq
  3f: 48                              rex.W