Re: Multiple potential races on vma->vm_flags

From: Sasha Levin
Date: Wed Sep 23 2015 - 17:30:37 EST

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In reply to: Oleg Nesterov: "Re: Multiple potential races on vma->vm_flags"
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On 09/15/2015 01:36 PM, Sasha Levin wrote:
> On 09/11/2015 09:27 PM, Hugh Dickins wrote:
>> > I'm inclined to echo Vlastimil's comment from earlier in the thread:
>> > sounds like an overkill, unless we find something more serious than this.
> I've modified my tests to stress the exit path of processes with many vmas,
> and hit the following NULL ptr deref (not sure if it's related to the original issue):
>
> [1181047.935563] kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
> [1181047.937223] Modules linked in:
> [1181047.937772] CPU: 4 PID: 21912 Comm: trinity-c341 Not tainted 4.3.0-rc1-next-20150914-sasha-00043-geddd763-dirty #2554
> [1181047.939387] task: ffff8804195c8000 ti: ffff880433f00000 task.ti: ffff880433f00000
> [1181047.940533] RIP: unmap_vmas (mm/memory.c:1337)
> [1181047.941842] RSP: 0000:ffff880433f078a8 EFLAGS: 00010206
> [1181047.942383] RAX: dffffc0000000000 RBX: ffff88041acd000a RCX: ffffffffffffffff
> [1181047.943091] RDX: 0000000000000099 RSI: ffff88041acd000a RDI: 00000000000004c8
> [1181047.943889] RBP: ffff880433f078d8 R08: ffff880415c59c58 R09: 0000000015c59e01
> [1181047.944604] R10: 0000000000000000 R11: 0000000000000001 R12: ffffffffffffffff
> [1181047.944833] pps pps0: PPS event at 21837.866101174
> [1181047.944838] pps pps0: capture assert seq #7188
> [1181047.946261] R13: 0000000000000000 R14: ffff880433f07910 R15: 0000000000002e0d
> [1181047.947005] FS: 0000000000000000(0000) GS:ffff880252000000(0000) knlGS:0000000000000000
> [1181047.947779] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [1181047.948361] CR2: 000000000097df90 CR3: 000000044e08c000 CR4: 00000000000006a0
> [1181047.949085] Stack:
> [1181047.949350] 0000000000000000 ffff880433f07910 1ffff100867e0f1e dffffc0000000000
> [1181047.950164] ffff8801d825d000 0000000000002e0d ffff880433f079d0 ffffffff9276c4ab
> [1181047.951070] ffff88041acd000a 0000000041b58ab3 ffffffff9ecd1a43 ffffffff9276c2a0
> [1181047.951906] Call Trace:
> [1181047.952201] exit_mmap (mm/mmap.c:2856)
> [1181047.952751] ? SyS_remap_file_pages (mm/mmap.c:2826)
> [1181047.953633] ? __khugepaged_exit (./arch/x86/include/asm/atomic.h:118 include/linux/sched.h:2557 mm/huge_memory.c:2169)
> [1181047.954281] ? rcu_read_lock_sched_held (kernel/rcu/update.c:109)
> [1181047.954936] ? kmem_cache_free (include/trace/events/kmem.h:143 mm/slub.c:2746)
> [1181047.955535] ? __khugepaged_exit (./arch/x86/include/asm/atomic.h:118 include/linux/sched.h:2557 mm/huge_memory.c:2169)
> [1181047.956204] mmput (include/linux/compiler.h:207 kernel/fork.c:735 kernel/fork.c:702)
> [1181047.956691] do_exit (./arch/x86/include/asm/bitops.h:311 include/linux/thread_info.h:91 kernel/exit.c:438 kernel/exit.c:733)
> [1181047.957241] ? lockdep_init (kernel/locking/lockdep.c:3298)
> [1181047.958005] ? mm_update_next_owner (kernel/exit.c:654)
> [1181047.959007] ? debug_smp_processor_id (lib/smp_processor_id.c:57)
> [1181047.959995] ? get_lock_stats (kernel/locking/lockdep.c:249)
> [1181047.960885] ? lockdep_init (kernel/locking/lockdep.c:3298)
> [1181047.961438] ? __raw_callee_save___pv_queued_spin_unlock (??:?)
> [1181047.962573] ? lock_release (kernel/locking/lockdep.c:3641)
> [1181047.963488] ? __raw_callee_save___pv_queued_spin_unlock (??:?)
> [1181047.964704] do_group_exit (./arch/x86/include/asm/current.h:14 kernel/exit.c:859)
> [1181047.965569] get_signal (kernel/signal.c:2353)
> [1181047.966430] do_signal (arch/x86/kernel/signal.c:709)
> [1181047.967241] ? do_readv_writev (include/linux/fsnotify.h:223 fs/read_write.c:821)
> [1181047.968169] ? v9fs_file_lock_dotl (fs/9p/vfs_file.c:407)
> [1181047.969126] ? vfs_write (fs/read_write.c:777)
> [1181047.969955] ? setup_sigcontext (arch/x86/kernel/signal.c:706)
> [1181047.970916] ? __raw_callee_save___pv_queued_spin_unlock (??:?)
> [1181047.972139] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
> [1181047.973489] ? _raw_spin_unlock_irq (./arch/x86/include/asm/preempt.h:95 include/linux/spinlock_api_smp.h:171 kernel/locking/spinlock.c:199)
> [1181047.974160] ? do_setitimer (include/linux/spinlock.h:357 kernel/time/itimer.c:227)
> [1181047.974818] ? check_preemption_disabled (lib/smp_processor_id.c:18)
> [1181047.975480] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
> [1181047.976142] prepare_exit_to_usermode (arch/x86/entry/common.c:251)
> [1181047.976784] syscall_return_slowpath (arch/x86/entry/common.c:318)
> [1181047.977473] int_ret_from_sys_call (arch/x86/entry/entry_64.S:282)
> [1181047.978116] Code: 08 80 3c 02 00 0f 85 22 01 00 00 48 8b 43 40 48 8d b8 c8 04 00 00 48 89 45 d0 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 ee 00 00 00 48 8b 45 d0 48 83 b8 c8 04 00 00
> All code
> ========
> 0: 08 80 3c 02 00 0f or %al,0xf00023c(%rax)
> 6: 85 22 test %esp,(%rdx)
> 8: 01 00 add %eax,(%rax)
> a: 00 48 8b add %cl,-0x75(%rax)
> d: 43 rex.XB
> e: 40 rex
> f: 48 8d b8 c8 04 00 00 lea 0x4c8(%rax),%rdi
> 16: 48 89 45 d0 mov %rax,-0x30(%rbp)
> 1a: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
> 21: fc ff df
> 24: 48 89 fa mov %rdi,%rdx
> 27: 48 c1 ea 03 shr $0x3,%rdx
> 2b:* 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) <-- trapping instruction
> 2f: 0f 85 ee 00 00 00 jne 0x123
> 35: 48 8b 45 d0 mov -0x30(%rbp),%rax
> 39: 48 83 b8 c8 04 00 00 cmpq $0x0,0x4c8(%rax)
> 40: 00
>
> Code starting with the faulting instruction
> ===========================================
> 0: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
> 4: 0f 85 ee 00 00 00 jne 0xf8
> a: 48 8b 45 d0 mov -0x30(%rbp),%rax
> e: 48 83 b8 c8 04 00 00 cmpq $0x0,0x4c8(%rax)
> 15: 00
> [1181047.981417] RIP unmap_vmas (mm/memory.c:1337)
> [1181047.982011] RSP <ffff880433f078a8>

Another similar trace where we see a problem during process exit:

[1922964.887922] kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
[1922964.890234] Modules linked in:
[1922964.890844] CPU: 1 PID: 21477 Comm: trinity-c161 Tainted: G W 4.3.0-rc2-next-20150923-sasha-00079-gec04207-dirty #2569
[1922964.892584] task: ffff880251858000 ti: ffff88009f258000 task.ti: ffff88009f258000
[1922964.893723] RIP: acct_collect (kernel/acct.c:542)
[1922964.895105] RSP: 0000:ffff88009f25f908 EFLAGS: 00010207
[1922964.895935] RAX: dffffc0000000000 RBX: 2ce0ffffffffffff RCX: 0000000000000000
[1922964.897008] RDX: ffff2152b153ffff RSI: 059c200000000000 RDI: 2ce1000000000007
[1922964.898091] RBP: ffff88009f25f9e8 R08: 0000000000000001 R09: 00000000000003ef
[1922964.899178] R10: ffffed014d7a3a01 R11: 0000000000000001 R12: ffff880082b485c0
[1922964.901643] R13: ffff2152b153ffff R14: 1ffff10013e4bf24 R15: ffff88009f25f9c0
[1922964.904396] FS: 00007f680d3f2700(0000) GS:ffff880108000000(0000) knlGS:0000000000000000
[1922964.907484] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[1922964.908489] CR2: 00007f680b7a3000 CR3: 00000000af748000 CR4: 00000000000006a0
[1922964.909626] Stack:
[1922964.910009] dffffc0000000000 ffff880251858000 0000000000000009 0000000041b58ab3
[1922964.913945] ffffffffa2ee6c6a ffffffff96561dc0 0000000041b58ab3 ffffffffa2ee6c6a
[1922964.915212] 0000000041b58ab3 ffffffffa2edfbb4 ffffffff9650ce50 0000000041b58ab3
[1922964.916489] Call Trace:
[1922964.916951] ? acct_exit_ns (kernel/acct.c:531)
[1922964.917859] ? hrtimer_get_remaining (kernel/time/hrtimer.c:1028)
[1922964.918895] ? get_signal (kernel/signal.c:2384)
[1922964.919821] ? creds_are_invalid (kernel/cred.c:709)
[1922964.921177] do_exit (kernel/exit.c:727)
[1922964.922022] ? lockdep_reset_lock (kernel/locking/lockdep.c:3105)
[1922964.923009] ? mm_update_next_owner (kernel/exit.c:654)
[1922964.924099] ? debug_smp_processor_id (lib/smp_processor_id.c:57)
[1922964.925237] ? lockdep_init (kernel/locking/lockdep.c:3298)
[1922964.926157] ? __raw_callee_save___pv_queued_spin_unlock (??:?)
[1922964.927223] do_group_exit (./arch/x86/include/asm/current.h:14 kernel/exit.c:859)
[1922964.928111] get_signal (kernel/signal.c:2307)
[1922964.929021] do_signal (arch/x86/kernel/signal.c:709)
[1922964.929902] ? do_readv_writev (include/linux/fsnotify.h:223 fs/read_write.c:821)
[1922964.930962] ? __generic_file_write_iter (mm/filemap.c:2684)
[1922964.932119] ? vfs_write (fs/read_write.c:777)
[1922964.933052] ? setup_sigcontext (arch/x86/kernel/signal.c:706)
[1922964.934061] ? __raw_callee_save___pv_queued_spin_unlock (??:?)
[1922964.935261] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
[1922964.936285] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2594 kernel/locking/lockdep.c:2636)
[1922964.937575] ? _raw_spin_unlock_irq (./arch/x86/include/asm/preempt.h:95 include/linux/spinlock_api_smp.h:171 kernel/locking/spinlock.c:199)
[1922964.938563] ? do_setitimer (include/linux/spinlock.h:357 kernel/time/itimer.c:227)
[1922964.939463] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63)
[1922964.940596] prepare_exit_to_usermode (arch/x86/entry/common.c:251)
[1922964.941645] syscall_return_slowpath (arch/x86/entry/common.c:318)
[1922964.942715] int_ret_from_sys_call (arch/x86/entry/entry_64.S:282)
[1922964.943706] Code: 02 00 0f 85 9d 05 00 00 48 8b 1b 48 85 db 0f 84 7b 05 00 00 48 b8 00 00 00 00 00 fc ff df 31 d2 48 8d 7b 08 48 89 fe 48 c1 ee 03 <80> 3c 06 00 0f 85 02 06 00 00 48 89 de 4c 8b 6b 08 48 c1 ee 03
All code
========
0: 02 00 add (%rax),%al
2: 0f 85 9d 05 00 00 jne 0x5a5
8: 48 8b 1b mov (%rbx),%rbx
b: 48 85 db test %rbx,%rbx
e: 0f 84 7b 05 00 00 je 0x58f
14: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
1b: fc ff df
1e: 31 d2 xor %edx,%edx
20: 48 8d 7b 08 lea 0x8(%rbx),%rdi
24: 48 89 fe mov %rdi,%rsi
27: 48 c1 ee 03 shr $0x3,%rsi
2b:* 80 3c 06 00 cmpb $0x0,(%rsi,%rax,1) <-- trapping instruction
2f: 0f 85 02 06 00 00 jne 0x637
35: 48 89 de mov %rbx,%rsi
38: 4c 8b 6b 08 mov 0x8(%rbx),%r13
3c: 48 c1 ee 03 shr $0x3,%rsi
...

Code starting with the faulting instruction
===========================================
0: 80 3c 06 00 cmpb $0x0,(%rsi,%rax,1)
4: 0f 85 02 06 00 00 jne 0x60c
a: 48 89 de mov %rbx,%rsi
d: 4c 8b 6b 08 mov 0x8(%rbx),%r13
11: 48 c1 ee 03 shr $0x3,%rsi
...
[1922964.948548] RIP acct_collect (kernel/acct.c:542)
[1922964.949552] RSP <ffff88009f25f908>

Thanks,
Sasha
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Next message: Arnd Bergmann: "Re: [PATCH v2 1/9] ARM: dts: consolidate aliases for Cygnus dt files"
Previous message: Arnd Bergmann: "Re: [PATCH v2 5/9] ARM: dts: Move all Cygnus peripherals into soc bus"
In reply to: Oleg Nesterov: "Re: Multiple potential races on vma->vm_flags"
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