Re: fanotify use after free.

[Jiri Kosina]

On Wed, 22 Jan 2014, Linus Torvalds wrote:

> > But refcounting seems like an overkill for this - there is exactly one
> > fanotify_response_event structure iff it is a permission event. So
> > something like the (completely untested) attached patch should fix the
> > problem. But I agree it's a bit ugly so we might want something different.
> > I'll try to think about something better tomorrow.
> 
> Ok, In the meantime, Dave, can you verify whether this hacky patch
> fixes your problem?

I reported the same slab corruption yesterday as well here:

	https://lkml.org/lkml/2014/1/22/173

With the patch applied, I am still seeing the slab corruption, preceeded 
by GPF (which is not there without the patch) in 
lockref_put_or_lock(&dentry->d_lockref) in dput():

 general protection fault: 0000 [#1] SMP 
 Modules linked in: tpm_tis(+) tpm wmi acpi_cpufreq autofs4 uhci_hcd ehci_hcd i915 drm_kms_helper drm i2c_algo_bit button usbcore video usb_common edd fan processor ata_generic thermal thermal_sys
 CPU: 1 PID: 275 Comm: systemd-readahe Not tainted 3.13.0-03478-g670d0ac #1
 Hardware name: LENOVO 7470BN2/7470BN2, BIOS 6DET38WW (2.02 ) 12/19/2008
 task: ffff880037c09150 ti: ffff88007359e000 task.ti: ffff88007359e000
 RIP: 0010:[<ffffffff810a51e7>]  [<ffffffff810a51e7>] do_raw_spin_lock+0x17/0x160
 RSP: 0018:ffff88007359fc78  EFLAGS: 00010286
 RAX: ffff880037c09150 RBX: 6b6b6b6b6b6b6beb RCX: 0000000000000000
 tpm_tis 00:09: 1.2 TPM (device-id 0x1020, rev-id 6)
 tpm_tis 00:09: Intel iTPM workaround enabled
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 6b6b6b6b6b6b6beb
 RBP: ffff88007359fc98 R08: 0000000000000002 R09: 0000000000000000
 R10: 0000000000000000 R11: 0000000000000000 R12: 6b6b6b6b6b6b6beb
 R13: ffff880037310690 R14: 0000000000000020 R15: ffff880036dbfc10
 FS:  00007fa953e4a700(0000) GS:ffff88007c280000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00007fff76a10258 CR3: 000000003659c000 CR4: 00000000000007e0
 Stack:
  6b6b6b6b6b6b6beb 6b6b6b6b6b6b6beb 6b6b6b6b6b6b6beb ffff880037310690
  ffff88007359fcb8 ffffffff8159c59c ffffffff812fe101 6b6b6b6b6b6b6beb
  ffff88007359fcd8 ffffffff812fe101 ffff88007359fd08 6b6b6b6b6b6b6b6b
 Call Trace:
  [<ffffffff8159c59c>] _raw_spin_lock+0x3c/0x50
  [<ffffffff812fe101>] ? lockref_put_or_lock+0x11/0x40
  [<ffffffff812fe101>] lockref_put_or_lock+0x11/0x40
  [<ffffffff811b1442>] dput+0x22/0x130
  [<ffffffff811a3d45>] path_put+0x15/0x30
  [<ffffffff811e0bc5>] fanotify_free_event+0x15/0x40
  [<ffffffff811dd7ac>] fsnotify_destroy_event+0x1c/0x30
  [<ffffffff811e1041>] fanotify_handle_event+0x341/0x390
  [<ffffffff811dd18b>] send_to_group+0xfb/0x180
  [<ffffffff811dd290>] ? fsnotify+0x80/0x2d0
  [<ffffffff811ab325>] ? do_filp_open+0x45/0xa0
  [<ffffffff811dd3d4>] fsnotify+0x1c4/0x2d0
  [<ffffffff811987ad>] do_sys_open+0x1ad/0x220
  [<ffffffff812fdd6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
  [<ffffffff81198859>] SyS_open+0x19/0x20
  [<ffffffff815a5222>] system_call_fastpath+0x16/0x1b
 Code: 0d 7e 81 48 89 df e8 29 ff ff ff eb 94 0f 1f 80 00 00 00 00 55 48 89 e5 48 83 ec 20 48 89 5d e8 4c 89 65 f0 48 89 fb 4c 89 6d f8 <81> 7f 04 ad 4e ad de 74 0c 48 c7 c6 b5 0d 7e 81 e8 f4 fe ff ff 
 RIP  [<ffffffff810a51e7>] do_raw_spin_lock+0x17/0x160
  RSP <ffff88007359fc78>
 ---[ end trace 7a918209ee213d28 ]---
 BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:20
 in_atomic(): 1, irqs_disabled(): 0, pid: 275, name: systemd-readahe
 INFO: lockdep is turned off.
 CPU: 1 PID: 275 Comm: systemd-readahe Tainted: G      D      3.13.0-03478-g670d0ac #1
 Hardware name: LENOVO 7470BN2/7470BN2, BIOS 6DET38WW (2.02 ) 12/19/2008
  ffff880037c09150 ffff88007359fa78 ffffffff8159702b ffff88007359fa98
  ffffffff8107f621 ffffffff81a3d000 ffff880037b98d90 ffff88007359fab8
  ffffffff8159b4ff ffff880037c09150 ffff880037c09150 ffff88007359fae8
 Call Trace:
  [<ffffffff8159702b>] dump_stack+0x72/0x87
  [<ffffffff8107f621>] __might_sleep+0xe1/0x100
  [<ffffffff8159b4ff>] down_read+0x1f/0x60
  [<ffffffff810627ff>] exit_signals+0x1f/0x140
  [<ffffffff81079491>] ? blocking_notifier_call_chain+0x11/0x20
  [<ffffffff81052844>] do_exit+0xb4/0x4b0
  [<ffffffff8159e23c>] oops_end+0xdc/0xe0
  [<ffffffff81005f86>] die+0x56/0x90
  [<ffffffff8159dea2>] do_general_protection+0x162/0x170
  [<ffffffff8159d40c>] ? restore_args+0x30/0x30
  [<ffffffff8159d592>] general_protection+0x22/0x30
  [<ffffffff810a51e7>] ? do_raw_spin_lock+0x17/0x160
  [<ffffffff8159c59c>] _raw_spin_lock+0x3c/0x50
  [<ffffffff812fe101>] ? lockref_put_or_lock+0x11/0x40
  [<ffffffff812fe101>] lockref_put_or_lock+0x11/0x40
  [<ffffffff811b1442>] dput+0x22/0x130
  [<ffffffff811a3d45>] path_put+0x15/0x30
  [<ffffffff811e0bc5>] fanotify_free_event+0x15/0x40
  [<ffffffff811dd7ac>] fsnotify_destroy_event+0x1c/0x30
  [<ffffffff811e1041>] fanotify_handle_event+0x341/0x390
  [<ffffffff811dd18b>] send_to_group+0xfb/0x180
  [<ffffffff811dd290>] ? fsnotify+0x80/0x2d0
  [<ffffffff811ab325>] ? do_filp_open+0x45/0xa0
  [<ffffffff811dd3d4>] fsnotify+0x1c4/0x2d0
  [<ffffffff811987ad>] do_sys_open+0x1ad/0x220
  [<ffffffff812fdd6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
  [<ffffffff81198859>] SyS_open+0x19/0x20
  [<ffffffff815a5222>] system_call_fastpath+0x16/0x1b
 note: systemd-readahe[275] exited with preempt_count 1
 BUG: scheduling while atomic: systemd-readahe/275/0x00000002
 INFO: lockdep is turned off.
 Modules linked in: tpm_tis(+) tpm wmi acpi_cpufreq autofs4 uhci_hcd ehci_hcd i915 drm_kms_helper drm i2c_algo_bit button usbcore video usb_common edd fan processor ata_generic thermal thermal_sys
 CPU: 1 PID: 275 Comm: systemd-readahe Tainted: G      D      3.13.0-03478-g670d0ac #1
 Hardware name: LENOVO 7470BN2/7470BN2, BIOS 6DET38WW (2.02 ) 12/19/2008
  ffff88007c293a00 ffff88007359f6f8 ffffffff8159702b ffff88007359f718
  ffffffff810810f1 ffff88007c293a00 0000000000000001 ffff88007359f848
  ffffffff8159789c ffff88007359f758 ffff88007359f768 ffff88007359e010
 Call Trace:
  [<ffffffff8159702b>] dump_stack+0x72/0x87
  [<ffffffff810810f1>] __schedule_bug+0x61/0x80
  [<ffffffff8159789c>] __schedule+0xbc/0x7c0
  [<ffffffff8105defc>] ? mod_timer+0x14c/0x1f0
  [<ffffffff815980e4>] schedule+0x24/0x70
  [<ffffffff81597205>] schedule_timeout+0x1c5/0x210
  [<ffffffff8159914f>] ? wait_for_completion+0xcf/0x120
  [<ffffffff810a0d8d>] ? trace_hardirqs_on+0xd/0x10
  [<ffffffff81599157>] wait_for_completion+0xd7/0x120
  [<ffffffff81083330>] ? try_to_wake_up+0x250/0x250
  [<ffffffff810b93bf>] ? srcu_reschedule+0x4f/0xf0
  [<ffffffff810b965c>] __synchronize_srcu+0xec/0x130
  [<ffffffff810b96e0>] ? srcu_barrier+0x10/0x10
  [<ffffffff810b96c8>] synchronize_srcu+0x18/0x20
  [<ffffffff811ddbdd>] fsnotify_destroy_group+0x1d/0x40
  [<ffffffff811dfdf1>] inotify_release+0x21/0x50
  [<ffffffff8119b2dd>] __fput+0xbd/0x2b0
  [<ffffffff8119b569>] ____fput+0x9/0x10
  [<ffffffff81070f41>] task_work_run+0xb1/0xe0
  [<ffffffff81052979>] do_exit+0x1e9/0x4b0
  [<ffffffff8159e23c>] oops_end+0xdc/0xe0
  [<ffffffff81005f86>] die+0x56/0x90
  [<ffffffff8159dea2>] do_general_protection+0x162/0x170
  [<ffffffff8159d40c>] ? restore_args+0x30/0x30
  [<ffffffff8159d592>] general_protection+0x22/0x30
  [<ffffffff810a51e7>] ? do_raw_spin_lock+0x17/0x160
  [<ffffffff8159c59c>] _raw_spin_lock+0x3c/0x50
  [<ffffffff812fe101>] ? lockref_put_or_lock+0x11/0x40
  [<ffffffff812fe101>] lockref_put_or_lock+0x11/0x40
  [<ffffffff811b1442>] dput+0x22/0x130
  [<ffffffff811a3d45>] path_put+0x15/0x30
  [<ffffffff811e0bc5>] fanotify_free_event+0x15/0x40
  [<ffffffff811dd7ac>] fsnotify_destroy_event+0x1c/0x30
  [<ffffffff811e1041>] fanotify_handle_event+0x341/0x390
  [<ffffffff811dd18b>] send_to_group+0xfb/0x180
  [<ffffffff811dd290>] ? fsnotify+0x80/0x2d0
  [<ffffffff811ab325>] ? do_filp_open+0x45/0xa0
  [<ffffffff811dd3d4>] fsnotify+0x1c4/0x2d0
  [<ffffffff811987ad>] do_sys_open+0x1ad/0x220
  [<ffffffff812fdd6e>] ? trace_hardirqs_on_thunk+0x3a/0x3f
  [<ffffffff81198859>] SyS_open+0x19/0x20
  [<ffffffff815a5222>] system_call_fastpath+0x16/0x1b
 ACPI: AC Adapter [AC] (on-line)
 Slab corruption (Tainted: G      D W   ): fanotify_event_info start=ffff880037310690, len=64
 Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
 Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
 030: 6b 6b 6b 6b 6b 6b 6b 6b 00 00 00 00 6b 6b 6b a5  kkkkkkkk....kkk.
 Prev obj: start=ffff880037310638, len=64
 Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
 Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
 Next obj: start=ffff8800373106e8, len=64
 Redzone: 0x9f911029d74e35b/0x9f911029d74e35b.
 Last user: [<ffffffff811e0bdd>](fanotify_free_event+0x2d/0x40)
 000: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk
 010: 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b  kkkkkkkkkkkkkkkk

-- 
Jiri Kosina
SUSE Labs
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