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Message-ID: <5142ABD3.4040106@gmail.com> Date: Fri, 15 Mar 2013 01:04:19 -0400 From: Sasha Levin <levinsasha928@...il.com> To: Dave Jones <davej@...hat.com>, Greg Kroah-Hartman <greg@...ah.com>, Linux Kernel <linux-kernel@...r.kernel.org> Subject: Re: use after free in sysfs_find_dirent On 03/15/2013 12:03 AM, Sasha Levin wrote: > 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 ]--- And on the bright side, unlike in Dave's case, similar issues reproduce rather easily over here: [ 117.001400] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 117.007659] Dumping ftrace buffer: [ 117.008300] (ftrace buffer empty) [ 117.008885] Modules linked in: [ 117.009397] CPU 0 [ 117.009700] Pid: 9168, comm: trinity-child11 Tainted: G W 3.9.0-rc2-next-20130314-sasha-00046-g3897511 #295 [ 117.010041] RIP: 0010:[<ffffffff812fa6e0>] [<ffffffff812fa6e0>] sysfs_dir_pos+0xa0/0x100 [ 117.010041] RSP: 0018:ffff8800796dde18 EFLAGS: 00010202 [ 117.010041] RAX: 6b6b6b6b6b6b6b6b RBX: 0000000000000000 RCX: ffff8800b853d8c8 [ 117.010041] RDX: 0000000051932d51 RSI: 000000006b6b6b6b RDI: 0000000000000000 [ 117.010041] RBP: ffff8800796dde48 R08: 2222222222222222 R09: 2222222222222222 [ 117.010041] R10: 2222222222222222 R11: 0000000000000000 R12: 0000000000000000 [ 117.010041] R13: 0000000000000000 R14: ffff8800a4a4b0b8 R15: ffff8800a4a4afd0 [ 117.010041] FS: 00007f943990a700(0000) GS:ffff8800bb800000(0000) knlGS:0000000000000000 [ 117.010041] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 117.010041] CR2: 0000000000000000 CR3: 000000007bea7000 CR4: 00000000000406f0 [ 117.010041] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 117.010041] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 117.010041] Process trinity-child11 (pid: 9168, threadinfo ffff8800796dc000, task ffff88008120b000) [ 117.010041] Stack: [ 117.010041] ffff8800a4a4b0b8 ffff8800a4a4afd0 ffff8800796dde48 ffffffff83d87edf [ 117.010041] ffff8800b853d6e0 ffff8800aa27d340 ffff8800796ddeb8 ffffffff812fa85d [ 117.010041] 2222222222222222 2222222222222222 ffff8800796dde98 ffffffff8128cca0 [ 117.010041] Call Trace: [ 117.010041] [<ffffffff83d87edf>] ? mutex_lock_nested+0x3f/0x50 [ 117.010041] [<ffffffff812fa85d>] sysfs_readdir+0x11d/0x280 [ 117.010041] [<ffffffff8128cca0>] ? filldir+0x100/0x100 [ 117.010041] [<ffffffff8128cca0>] ? filldir+0x100/0x100 [ 117.010041] [<ffffffff8128cf18>] vfs_readdir+0x78/0xc0 [ 117.010041] [<ffffffff8117ad3d>] ? trace_hardirqs_on+0xd/0x10 [ 117.010041] [<ffffffff8128d190>] SyS_getdents64+0x90/0x120 [ 117.010041] [<ffffffff83d946d8>] tracesys+0xe1/0xe6 [ 117.010041] Code: 00 00 00 48 85 c9 74 6d 48 39 59 68 75 45 eb 65 0f 1f 00 48 81 fa fe ff ff 7f 7f 59 48 8b 86 88 00 00 00 48 85 c0 74 4d 0f 1f 00 <8b> 70 28 48 8d 48 b8 48 39 f2 7d 0c 48 8b 40 10 eb 0c 66 0f 1f [ 117.010041] RIP [<ffffffff812fa6e0>] sysfs_dir_pos+0xa0/0x100 [ 117.010041] RSP <ffff8800796dde18> [ 117.058487] ---[ end trace 1a817146a00445c0 ]--- 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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