Re: KASAN: use-after-free Read in irq_bypass_register_consumer

From: Dmitry Vyukov
Date: Wed Nov 01 2017 - 16:19:01 EST

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In reply to: syzbot: "KASAN: use-after-free Read in irq_bypass_register_consumer"
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On Wed, Nov 1, 2017 at 11:17 PM, syzbot
<bot+9a592b2d4f3c5d4c93adef9de16ded0105530914@xxxxxxxxxxxxxxxxxxxxxxxxx>
wrote:
> Hello,
>
> syzkaller hit the following crash on
> aae4e7a8bc44722fe70d58920a36916b1043195e
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4f0/0x500
> virt/lib/irqbypass.c:198
> Read of size 8 at addr ffff8801cf1d9178 by task syzkaller948360/3420
>
> CPU: 1 PID: 3420 Comm: syzkaller948360 Not tainted 4.13.0-rc4+ #23
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
> __dump_stack lib/dump_stack.c:16 [inline]
> dump_stack+0x194/0x257 lib/dump_stack.c:52
> print_address_description+0x7f/0x260 mm/kasan/report.c:252
> kasan_report_error mm/kasan/report.c:351 [inline]
> kasan_report+0x24e/0x340 mm/kasan/report.c:409
> __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
> irq_bypass_register_consumer+0x4f0/0x500 virt/lib/irqbypass.c:198
> kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
> kvm_irqfd+0x137a/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
> kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3029
> vfs_ioctl fs/ioctl.c:45 [inline]
> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
> SYSC_ioctl fs/ioctl.c:700 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
> entry_SYSCALL_64_fastpath+0x1f/0xbe
> RIP: 0033:0x4460d9
> RSP: 002b:00007f24ae19adc8 EFLAGS: 00000202 ORIG_RAX: 0000000000000010
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004460d9
> RDX: 000000002000d000 RSI: 000000004020ae76 RDI: 000000000000002b
> RBP: 0000000000000086 R08: 00007f24ae19b700 R09: 00007f24ae19b700
> R10: 00007f24ae19b700 R11: 0000000000000202 R12: 0000000000000000
> R13: 00007ffe1847ef3f R14: 00007f24ae19b9c0 R15: 0000000000000000
>
> Allocated by task 3420:
> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
> save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_kmalloc+0xaa/0xd0 mm/kasan/kasan.c:551
> kmem_cache_alloc_trace+0x101/0x6f0 mm/slab.c:3627
> kmalloc include/linux/slab.h:493 [inline]
> kzalloc include/linux/slab.h:666 [inline]
> kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
> kvm_irqfd+0x16c/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
> kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3029
> vfs_ioctl fs/ioctl.c:45 [inline]
> do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:685
> SYSC_ioctl fs/ioctl.c:700 [inline]
> SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
> entry_SYSCALL_64_fastpath+0x1f/0xbe
>
> Freed by task 24:
> save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
> save_stack+0x43/0xd0 mm/kasan/kasan.c:447
> set_track mm/kasan/kasan.c:459 [inline]
> kasan_slab_free+0x6e/0xc0 mm/kasan/kasan.c:524
> __cache_free mm/slab.c:3503 [inline]
> kfree+0xd3/0x260 mm/slab.c:3820
> irqfd_shutdown+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
> process_one_work+0xbf3/0x1bc0 kernel/workqueue.c:2097
> worker_thread+0x223/0x1860 kernel/workqueue.c:2231
> kthread+0x35e/0x430 kernel/kthread.c:231
> ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:425
>
> The buggy address belongs to the object at ffff8801cf1d9000
> which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 376 bytes inside of
> 512-byte region [ffff8801cf1d9000, ffff8801cf1d9200)
> The buggy address belongs to the page:
> page:ffffea000654e778 count:1 mapcount:0 mapping:ffff8801cf1d9000 index:0x0
> flags: 0x200000000000100(slab)
> raw: 0200000000000100 ffff8801cf1d9000 0000000000000000 0000000100000006
> raw: ffffea000654e648 ffffea0006560c48 ffff8801dbc00600
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
> ffff8801cf1d9000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801cf1d9080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>>
>> ffff8801cf1d9100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>
> ^
> ffff8801cf1d9180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801cf1d9200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================

Still happens on newer commits, e.g. on linux-next
36ef71cae353f88fd6e095e2aaa3e5953af1685d (Oct 19)

==================================================================
BUG: KASAN: use-after-free in list_add include/linux/list.h:63 [inline]
BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4e4/0x530
virt/lib/irqbypass.c:217
Write of size 8 at addr ffff880067e363e8 by task a.out/12001

CPU: 1 PID: 12001 Comm: a.out Not tainted 4.14.0-rc5-next-20171018 #15
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x1a8/0x272 lib/dump_stack.c:52
print_address_description+0x6c/0x204 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x16e/0x270 mm/kasan/report.c:409
__asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
list_add include/linux/list.h:63 [inline]
irq_bypass_register_consumer+0x4e4/0x530 virt/lib/irqbypass.c:217
kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
kvm_irqfd+0x14e7/0x1e60 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
kvm_vm_ioctl+0xa15/0x1dc0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2988
vfs_ioctl fs/ioctl.c:45 [inline]
file_ioctl fs/ioctl.c:499 [inline]
do_vfs_ioctl+0x1cf/0x16b0 fs/ioctl.c:683
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0xb6/0xe0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x44c969
RSP: 002b:00007fc56c43edb8 EFLAGS: 00000297 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000044c969
RDX: 0000000020025fe0 RSI: 000000004020ae76 RDI: 0000000000000005
RBP: 0000000000000086 R08: 00007fc56c43f700 R09: 0000000000000000
R10: 00007fc56c43f700 R11: 0000000000000297 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fc56c43f9c0 R15: 00007fc56c43f700

Allocated by task 12001:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x140/0x740 mm/slab.c:3614
kmalloc include/linux/slab.h:502 [inline]
kzalloc include/linux/slab.h:691 [inline]
kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:296 [inline]
kvm_irqfd+0x187/0x1e60 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
kvm_vm_ioctl+0xa15/0x1dc0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2988
vfs_ioctl fs/ioctl.c:45 [inline]
file_ioctl fs/ioctl.c:499 [inline]
do_vfs_ioctl+0x1cf/0x16b0 fs/ioctl.c:683
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0xb6/0xe0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 1338:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3492 [inline]
kfree+0xca/0x250 mm/slab.c:3807
irqfd_shutdown+0x13a/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
process_one_work+0xb70/0x1ac0 kernel/workqueue.c:2112
worker_thread+0x223/0x1ac0 kernel/workqueue.c:2246
kthread+0x38f/0x470 kernel/kthread.c:242
ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:431

The buggy address belongs to the object at ffff880067e36280
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 360 bytes inside of
512-byte region [ffff880067e36280, ffff880067e36480)
The buggy address belongs to the page:
page:ffffea00019f8d80 count:1 mapcount:0 mapping:ffff880067e36000 index:0x0
flags: 0x100000000000100(slab)
raw: 0100000000000100 ffff880067e36000 0000000000000000 0000000100000006
raw: ffffea0001a945e0 ffffea0001a153a0 ffff88006c400940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff880067e36280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880067e36300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880067e36380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff880067e36400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880067e36480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

> ---
> This bug is generated by a dumb bot. It may contain errors.
> See https://goo.gl/tpsmEJ for details.
> Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
> Please credit me with: Reported-by: syzbot <syzkaller@xxxxxxxxxxxxxxxx>
>
> syzbot will keep track of this bug report.
> Once a fix for this bug is committed, please reply to this email with:
> #syz fix: exact-commit-title
> To mark this as a duplicate of another syzbot report, please reply with:
> #syz dup: exact-subject-of-another-report
> If it's a one-off invalid bug report, please reply with:
> #syz invalid
> Note: if the crash happens again, it will cause creation of a new bug
> report.
> Note: all commands must start from beginning of the line.
>
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Next message: Mike Galbraith: "Re: [PATCH RFC 1/2] sched: Minimize the idle cpu selection race window."
Previous message: syzbot: "KASAN: use-after-free Read in irq_bypass_register_consumer"
In reply to: syzbot: "KASAN: use-after-free Read in irq_bypass_register_consumer"
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