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Date: Wed, 28 May 2014 22:31:38 -0400 From: Sasha Levin <sasha.levin@...cle.com> To: Peter Zijlstra <peterz@...radead.org> CC: Ingo Molnar <mingo@...nel.org>, acme@...stprotocols.net, LKML <linux-kernel@...r.kernel.org>, Thomas Gleixner <tglx@...utronix.de>, Dave Jones <davej@...hat.com> Subject: Re: perf: use after free in perf_remove_from_context On 05/28/2014 07:52 PM, Sasha Levin wrote: > On 05/14/2014 12:35 PM, Peter Zijlstra wrote: >> On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote: >>>> -----BEGIN PGP SIGNED MESSAGE----- >>>> Hash: SHA1 >>>> >>>> On 05/14/2014 12:29 PM, Peter Zijlstra wrote: >>>>>> On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote: >>>>>>>> Hi all, >>>>>>>> >>>>>>>> While fuzzing with trinity inside a KVM tools guest running the latest -next kernel I've stumbled on the following spew. Maybe related to the very recent change in freeing on task exit? >>>>>>>> >>>>>>>> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379] (ftrace buffer empty) [ 2509.830379] Modules linked in: [ 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G W 3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456 >>>>>> >>>>>> Any particular trinity setup? And would you happen to have the seed of that run? >>>> >>>> Nothing special about trinity options. 400 threads and blacklisting some of the >>>> destructive syscalls (umount, reboot, etc). >>>> >>>> I don't have the seed, but that problem did reproduce again tonight so I can test >>>> out debug code if you have something in mind. >> Nah, I drew a pretty big blank, which is why I wanted to see if I could >> reproduce. If you could share your trinity cmdline I'd be much obliged. >> While I did manage to clone (the repo moved since last time) and build >> it, I'm not really that handy with it and want to avoid destroying my >> machine if possible ;-) > > Anything I could do to help out with this? It reproduces pretty easily on my > configuration so I'd be happy to test out whatever might help. I've just had this: [ 591.111854] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 591.121057] Dumping ftrace buffer: [ 591.121057] (ftrace buffer empty) [ 591.121057] Modules linked in: [ 591.121057] CPU: 14 PID: 10272 Comm: trinity-c230 Tainted: G W 3.15.0-rc7-next-20140528-sasha-00019-gd193e91-dirty #545 [ 591.121057] task: ffff8802df0d3000 ti: ffff8802df0fe000 task.ti: ffff8802df0fe000 [ 591.129130] RIP: perf_event_exit_task (kernel/events/core.c:7492 kernel/events/core.c:7524) [ 591.129130] RSP: 0000:ffff8802df0ffe28 EFLAGS: 00010246 [ 591.129130] RAX: 0000000000000000 RBX: ffff8802df0d3000 RCX: 0000000000000001 [ 591.129130] RDX: 0000000000000000 RSI: ffffffff97088100 RDI: 0000000000000282 [ 591.129130] RBP: ffff8802df0ffe98 R08: 0000000000000000 R09: 0000000000000000 [ 591.129130] R10: 0000000000000001 R11: 0000000000000000 R12: 6b6b6b6b6b6b6b6b [ 591.129130] R13: 6b6b6b6b6b6b6b6b R14: ffff8806c9bfd550 R15: 0000000000000001 [ 591.129130] FS: 00007f4b26866700(0000) GS:ffff88036ae00000(0000) knlGS:0000000000000000 [ 591.129130] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b [ 591.129130] CR2: 0000000001a3a9f8 CR3: 000000001702c000 CR4: 00000000000006a0 [ 591.129130] Stack: [ 591.129130] ffff8802df0ffe48 ffff8802df09cce0 ffff8802fdf99488 ffff8802fdf99290 [ 591.129130] ffff8806c9bfd5a8 ffff8806c9bfd670 ffff8802df0ffe88 6b6b6b6b6b6b6b6b [ 591.129130] ffff8802df0ffe98 0000000000000001 0000000000000001 ffff8802df0d3000 [ 591.129130] Call Trace: [ 591.129130] do_exit (kernel/exit.c:766) [ 591.129130] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) [ 591.129130] ? trace_hardirqs_on_caller (kernel/locking/lockdep.c:2557 kernel/locking/lockdep.c:2599) [ 591.129130] ? trace_hardirqs_on (kernel/locking/lockdep.c:2607) [ 591.129130] do_group_exit (kernel/exit.c:884) [ 591.129130] SyS_exit_group (kernel/exit.c:895) [ 591.129130] tracesys (arch/x86/kernel/entry_64.S:542) [ 591.129130] Code: a0 02 00 00 49 89 95 a8 02 00 00 4c 8b 45 a0 4c 89 c7 e8 11 c2 2c 03 48 8b 45 a8 48 89 c7 e8 15 7c ff ff 4c 89 ef e8 bd 7b ff ff <49> 8b 45 00 48 89 45 c8 4c 8b 6d c8 e8 cc 19 f6 ff 85 c0 74 0e All code ======== 0: a0 02 00 00 49 89 95 movabs 0x2a8958949000002,%al 7: a8 02 9: 00 00 add %al,(%rax) b: 4c 8b 45 a0 mov -0x60(%rbp),%r8 f: 4c 89 c7 mov %r8,%rdi 12: e8 11 c2 2c 03 callq 0x32cc228 17: 48 8b 45 a8 mov -0x58(%rbp),%rax 1b: 48 89 c7 mov %rax,%rdi 1e: e8 15 7c ff ff callq 0xffffffffffff7c38 23: 4c 89 ef mov %r13,%rdi 26: e8 bd 7b ff ff callq 0xffffffffffff7be8 2b:* 49 8b 45 00 mov 0x0(%r13),%rax <-- trapping instruction 2f: 48 89 45 c8 mov %rax,-0x38(%rbp) 33: 4c 8b 6d c8 mov -0x38(%rbp),%r13 37: e8 cc 19 f6 ff callq 0xfffffffffff61a08 3c: 85 c0 test %eax,%eax 3e: 74 0e je 0x4e ... Code starting with the faulting instruction =========================================== 0: 49 8b 45 00 mov 0x0(%r13),%rax 4: 48 89 45 c8 mov %rax,-0x38(%rbp) 8: 4c 8b 6d c8 mov -0x38(%rbp),%r13 c: e8 cc 19 f6 ff callq 0xfffffffffff619dd 11: 85 c0 test %eax,%eax 13: 74 0e je 0x23 ... [ 591.129130] RIP perf_event_exit_task (kernel/events/core.c:7492 kernel/events/core.c:7524) [ 591.129130] RSP <ffff8802df0ffe28> Seems similar enough. Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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