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SubjectRe: BUG: unable to handle kernel NULL pointer dereference in sctp_sched_dequeue_common
On Tue, Jul 12, 2022 at 2:52 AM Wei Chen <harperchen1110@gmail.com> wrote:
>
> 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@gmail.com>
>
> 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_stream_init() is also called in processing SCTP_CMD_PEER_INIT
generated in sctp_sf_do_5_1C_ack(). At that time some chunk might be
already in the outq and stream outq. Failure in sctp_stream_init() will
cause stream->out to be freed, which still holds some schedule information.

So 2 things should be done when this happens:
1. call sctp_stream_free() in err path to avoid memleak in
SCTP_SO(stream, i)->ext in sctp_stream_init().
2. set asoc->outqueue.sched back to &sctp_sched_fcfs to fix the
scheduler's dequeue crash.

Will prepare a fix.
Thanks.

> 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

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