Re: use after free in sysfs_find_dirent

[Ming Lei]

Hi,

On Fri, Mar 15, 2013 at 1:04 PM, Sasha Levin <levinsasha928@xxxxxxxxx> wrote:
> On 03/15/2013 12:03 AM, Sasha Levin wrote:
>>
>> [  350.140100] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
>> [  350.141468] Dumping ftrace buffer:
>> [  350.142048]    (ftrace buffer empty)
>> [  350.142619] Modules linked in:
>> [  350.143128] CPU 0
>> [  350.143434] Pid: 25064, comm: trinity-child14 Tainted: G        W    3.9.0-rc2-next-20130314-sasha-00046-g3897511 #295
>> [  350.145415] RIP: 0010:[<ffffffff819ebfb3>]  [<ffffffff819ebfb3>] rb_next+0x23/0x60
>> [  350.146680] RSP: 0018:ffff88007b9dde48  EFLAGS: 00010202
>> [  350.147528] RAX: 6b6b6b6b6b6b6b6b RBX: ffff8800b8524b70 RCX: ffff8800b8524b70
>> [  350.148738] RDX: 6b6b6b6b6b6b6b6b RSI: ffff8800b63b96e0 RDI: ffff8800b8524bb8
>> [  350.149939] RBP: ffff88007b9dde48 R08: 2222222222222222 R09: 2222222222222222
>> [  350.150035] R10: 2222222222222222 R11: 0000000000000000 R12: ffff88008c5cb180
>> [  350.150035] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000010
>> [  350.150035] FS:  00007fec4eae2700(0000) GS:ffff8800bb800000(0000) knlGS:0000000000000000
>> [  350.150035] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [  350.150035] CR2: 0000000000000001 CR3: 000000007c32d000 CR4: 00000000000406f0
>> [  350.150035] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> [  350.150035] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>> [  350.150035] Process trinity-child14 (pid: 25064, threadinfo ffff88007b9dc000, task ffff880096413000)
>> [  350.150035] Stack:
>> [  350.150035]  ffff88007b9ddeb8 ffffffff812fa959 2222222222222222 2222222200000008
>> [  350.150035]  000000000000293e ffffffff8128cca0 ffff88007b9ddf28 ffff8800b63b96e0
>> [  350.150035]  ffff8800a14e9b78 ffff88008c5cb180 ffff88007b9ddf28 ffffffff8128cca0
>> [  350.150035] Call Trace:
>> [  350.150035]  [<ffffffff812fa959>] sysfs_readdir+0x219/0x280
>> [  350.150035]  [<ffffffff8128cca0>] ? filldir+0x100/0x100
>> [  350.150035]  [<ffffffff8128cca0>] ? filldir+0x100/0x100
>> [  350.150035]  [<ffffffff8128cf18>] vfs_readdir+0x78/0xc0
>> [  350.150035]  [<ffffffff8117ad3d>] ? trace_hardirqs_on+0xd/0x10
>> [  350.150035]  [<ffffffff8128d190>] SyS_getdents64+0x90/0x120
>> [  350.150035]  [<ffffffff83d946d8>] tracesys+0xe1/0xe6
>> [  350.150035] Code: 85 d2 75 f4 5d c3 66 90 55 31 c0 48 8b 17 48 89 e5 48 39 d7 74 4a 48 8b 47 08 48 85 c0 75 0c eb 17 0f 1f 80
>> 00 00 00 00 48 89 d0 <48> 8b 50 10 48 85 d2 75 f4 eb 2a 66 90 48 89 d1 48 83 e1 fc 74
>> [  350.150035] RIP  [<ffffffff819ebfb3>] rb_next+0x23/0x60
>> [  350.150035]  RSP <ffff88007b9dde48>
>> [  350.179705] ---[ end trace a39f58a515b594d5 ]---
>
> And on the bright side, unlike in Dave's case, similar issues reproduce rather easily
> over here:

Could you share how to reproduce that easily?

Thanks,
-- 
Ming Lei
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