Re: use after free in sysfs_find_dirent

[Sasha Levin]

On 03/07/2013 01:26 AM, Dave Jones wrote:
> On Thu, Mar 07, 2013 at 02:02:30PM +0800, Greg Kroah-Hartman wrote:
>  > On Thu, Mar 07, 2013 at 12:28:54AM -0500, Dave Jones wrote:
>  > > general protection fault: 0000 [#1] PREEMPT SMP 
>  > > Modules linked in: vmw_vsock_vmci_transport vmw_vmci vsock bnep fuse rfcomm hidp l2tp_ppp l2tp_core 8021q garp mrp dlci pppoe pppox ppp_generic slhc scsi_transport_iscsi rose caif_socket caif can_raw bridge af_key can_bcm llc2 stp can netrom phonet af_rxrpc nfnetlink ipt_ULOG x25 rds irda crc_ccitt ax25 ipx p8023 p8022 decnet atm appletalk psnap llc nfc lockd sunrpc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_conntrack nf_conntrack ip6table_filter ip6_tables snd_hda_codec_realtek snd_hda_intel snd_hda_codec snd_pcm btusb snd_page_alloc bluetooth snd_timer snd microcode rfkill usb_debug serio_raw pcspkr edac_core soundcore vhost_net tun r8169 macvtap macvlan mii kvm_amd kvm
>  > > CPU 0 
>  > > Pid: 23476, comm: trinity-child1 Not tainted 3.9.0-rc1+ #69 Gigabyte Technology Co., Ltd. GA-MA78GM-S2H/GA-MA78GM-S2H
>  > > RIP: 0010:[<ffffffff812356b7>]  [<ffffffff812356b7>] sysfs_find_dirent+0x47/0xf0
>  > > RSP: 0018:ffff88000585bd68  EFLAGS: 00010202
>  > > RAX: 0000000094be55f6 RBX: 6b6b6b6b6b6b6b6b RCX: 000000006b6b6b6b
>  > > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
>  > > RBP: ffff88000585bd88 R08: 0000000000000000 R09: 0000000000000000
>  > > R10: 0000000000000000 R11: 0000000000000000 R12: 000000000029c161
>  > > R13: ffff8800a8918288 R14: 0000000000000000 R15: 0000000000000009
>  > > FS:  00007fa12651e740(0000) GS:ffff88012ae00000(0000) knlGS:0000000000000000
>  > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  > > CR2: 0000000000000010 CR3: 000000001a128000 CR4: 00000000000007f0
>  > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>  > > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
>  > > Process trinity-child1 (pid: 23476, threadinfo ffff88000585a000, task ffff8800cd454920)
>  > > Stack:
>  > >  ffff880128edc1e8 ffff8800a8918250 fffffffffffffffe ffff88012265f430
>  > >  ffff88000585bdb8 ffffffff812357cd ffff8800a8918250 ffff8801226514d0
>  > >  ffff88000585bf38 0000000000000000 ffff88000585bde8 ffffffff811bb30d
>  > > Call Trace:
>  > >  [<ffffffff812357cd>] sysfs_lookup+0x6d/0xe0
>  > >  [<ffffffff811bb30d>] lookup_real+0x1d/0x60
>  > >  [<ffffffff811bb528>] __lookup_hash+0x38/0x50
>  > >  [<ffffffff811bb559>] lookup_hash+0x19/0x20
>  > >  [<ffffffff811be993>] kern_path_create+0x93/0x170
>  > >  [<ffffffff811bce46>] ? getname_flags.part.32+0x86/0x150
>  > >  [<ffffffff811beaba>] user_path_create+0x4a/0x70
>  > >  [<ffffffff811c1a09>] sys_mkdirat+0x39/0xe0
>  > >  [<ffffffff816cd942>] system_call_fastpath+0x16/0x1b
>  > > Code: 00 48 8b 9f 88 00 00 00 f6 c4 0f 0f 95 c0 48 85 f6 0f 95 c2 38 d0 75 79 4c 89 ee 4c 89 f7 e8 91 ef ff ff 41 89 c4 48 85 db 74 1d <8b> 4b 28 41 39 cc 74 21 44 89 e0 29 c8 83 f8 00 7c 2c 74 45 48 
>  > > RIP  [<ffffffff812356b7>] sysfs_find_dirent+0x47/0xf0
>  > >  RSP <ffff88000585bd68>
>  > > ---[ end trace 4ba97703eaafbb8b ]---
>  > 
>  > Any hint as to what was happening here when this crashed?
> 
> Given I haven't seen this (or the other sysfs bug) before today, I'm going
> to assume it's due to one of the features I added to trinity today.
> 
> 1. Instead of just relying on filenames it gathers from sysfs on startup,
>    it now also generates mangled variants of them.
>    (Appending a / followed by garbage for eg)
> 
> 2. When a syscall wants a page of memory, it now sometimes hands it one
>    filled with malformed UTF-8 characters.
> 
> 3. A combo of the above, that garbage appended to a pathname may be unicode junk.
> 
> Could be some of those that caused these bugs.
> 
> I just retried rerunning the test a few times.  Every time I run for a while
> I end up with different crashes.  It's raining bugs over here.
> (Here's another sysfs one below)
> 
> Running 'trinity -c mkdirat -V /sys' doesn't seem to trigger it, so it's an
> interaction with something else maybe.
> 
> The one common thing here is that 6b6b6b6b6b6b6b6b showing up in every trace,
> suggesting a use-after-free bugs. They may all be different manifestations
> of the same underlying bug if there's some kind of refcounting bug perhaps.
> (This may also be why telling it to do just mkdirat isn't triggering it,
>  if it's racing with some other operation)
> 
> Getting this stuff easily reproducable is pretty hard. The best I can offer
> right now is that it seems to trigger *something* bad quickly, even if it's
> not necessarily the exact same trace.

I've hit something similar, but I suspect it's the same issue:

[  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 ]---



Thanks,
Sasha

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