Re: general protection fault in __bpf_map_put

[Daniel Borkmann]

On 01/13/2018 08:16 AM, Dmitry Vyukov wrote:
> On Wed, Jan 10, 2018 at 1:58 PM, syzbot
> <syzbot+d2f5524fb46fd3b312ee@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>> Hello,
>>
>> syzkaller hit the following crash on
>> b4464bcab38d3f7fe995a7cb960eeac6889bec08
>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
>> compiler: gcc (GCC) 7.1.1 20170620
>> .config is attached
>> Raw console output is attached.
>> C reproducer is attached
>> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
>> for information about syzkaller reproducers
>>
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+d2f5524fb46fd3b312ee@xxxxxxxxxxxxxxxxxxxxxxxxx
>> It will help syzbot understand when the bug is fixed. See footer for
>> details.
>> If you forward the report, please keep this part and the footer.
> 
> Daniel, is it the same bug that was fixed by "bpf, array: fix overflow
> in max_entries and undefined behavior in index_mask"?

Yes, fixed by:

https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/commit/?id=bbeb6e4323dad9b5e0ee9f60c223dd532e2403b1

>> audit: type=1400 audit(1515571663.627:11): avc:  denied  { map_read
>> map_write } for  pid=3537 comm="syzkaller597104"
>> scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
>> tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf
>> permissive=1
>> kasan: CONFIG_KASAN_INLINE enabled
>> kasan: GPF could be caused by NULL-ptr deref or user memory access
>> general protection fault: 0000 [#1] SMP KASAN
>> Dumping ftrace buffer:
>>    (ftrace buffer empty)
>> Modules linked in:
>> CPU: 1 PID: 23 Comm: kworker/1:1 Not tainted 4.15.0-rc7-next-20180110+ #93
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Workqueue: events bpf_map_free_deferred
>> RIP: 0010:__bpf_map_put+0x64/0x2e0 kernel/bpf/syscall.c:233
>> RSP: 0018:ffff8801d98b7458 EFLAGS: 00010293
>> RAX: ffff8801d98ac600 RBX: ad6001bc00000dd1 RCX: ffffffff817e4454
>> RDX: 0000000000000000 RSI: 0000000000000001 RDI: ad6001bc00000dd1
>> RBP: ffff8801d98b74e8 R08: 1ffff1003b316e6a R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003b316e8c
>> R13: dffffc0000000000 R14: dffffc0000000000 R15: 0000000000000001
>> FS:  0000000000000000(0000) GS:ffff8801db300000(0000) knlGS:0000000000000000
>> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> CR2: 00000000204f9fe4 CR3: 0000000006822003 CR4: 00000000001606e0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>  bpf_map_put+0x1a/0x20 kernel/bpf/syscall.c:243
>>  bpf_map_fd_put_ptr+0x15/0x20 kernel/bpf/map_in_map.c:96
>>  fd_array_map_delete_elem kernel/bpf/arraymap.c:420 [inline]
>>  bpf_fd_array_map_clear kernel/bpf/arraymap.c:461 [inline]
>>  array_of_map_free+0x100/0x180 kernel/bpf/arraymap.c:618
>>  bpf_map_free_deferred+0xb0/0xe0 kernel/bpf/syscall.c:217
>>  process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2112
>>  worker_thread+0x223/0x1990 kernel/workqueue.c:2246
>>  kthread+0x33c/0x400 kernel/kthread.c:238
>>  ret_from_fork+0x4b/0x60 arch/x86/entry/entry_64.S:547
>> Code: b5 41 48 c7 45 80 1d 2c 59 86 48 c7 45 88 f0 43 7e 81 c7 00 f1 f1 f1
>> f1 c7 40 04 00 f2 f2 f2 c7 40 08 f3 f3 f3 f3 e8 9c 1e f2 ff <f0> ff 4b 48 74
>> 2f e8 91 1e f2 ff 48 b8 00 00 00 00 00 fc ff df
>> RIP: __bpf_map_put+0x64/0x2e0 kernel/bpf/syscall.c:233 RSP: ffff8801d98b7458
>> ---[ end trace 61592f27aaa1e096 ]---
>> Kernel panic - not syncing: Fatal exception
>> Dumping ftrace buffer:
>>    (ftrace buffer empty)
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
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