The root cause is that kvm_irqfd_assign() and kvm_irqfd_deassign() can't
be run in parallel. Some data structure(e.g, irqfd->consumer) will be
crashed because irqfd may be freed in deassign path before they are used
in assign path. The other data maybe used in deassign path before
initialization. Syzbot test hit such case. Add mutx between
kvm_irqfd_assign() and kvm_irqfd_deassign() can fix such issue. Will
send patch to fix it.
On 12/16/2017 12:53 PM, Tianyu Lan wrote:
I reproduced the issue. Will have a look.
-- Best regards Tianyu Lan 2017-12-15 18:14 GMT+08:00 syzbot
<bot+7ad82526b98c64c90062275162dacfa48c20dbd3@xxxxxxxxxxxxxxxxxxxxxxxxx>:
syzkaller has found reproducer for the following crash on
82bcf1def3b5f1251177ad47c44f7e17af039b4b
git://git.cmpxchg.org/linux-mmots.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. Seehttps://goo.gl/kgGztJ
for information about syzkaller reproducers
==================================================================
BUG: KASAN: use-after-free in __list_add include/linux/list.h:64 [inline]
BUG: KASAN: use-after-free in list_add include/linux/list.h:79 [inline]
BUG: KASAN: use-after-free in irq_bypass_register_consumer+0x4b4/0x500
virt/lib/irqbypass.c:217
Write of size 8 at addr ffff8801cdf51180 by task syzkaller436086/15031
CPU: 1 PID: 15031 Comm: syzkaller436086 Not tainted 4.15.0-rc2-mm1+ #39
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_address_description+0x73/0x250 mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report+0x25b/0x340 mm/kasan/report.c:409
__asan_report_store8_noabort+0x17/0x20 mm/kasan/report.c:435
__list_add include/linux/list.h:64 [inline]
list_add include/linux/list.h:79 [inline]
irq_bypass_register_consumer+0x4b4/0x500 virt/lib/irqbypass.c:217
kvm_irqfd_assign arch/x86/kvm/../../../virt/kvm/eventfd.c:417 [inline]
kvm_irqfd+0x137f/0x1d50 arch/x86/kvm/../../../virt/kvm/eventfd.c:572
kvm_vm_ioctl+0x1079/0x1c40 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2992
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x44d379
RSP: 002b:00007fc5ff9a9d08 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fc5ff9aa700 RCX: 000000000044d379
RDX: 0000000020080fe0 RSI: 000000004020ae76 RDI: 0000000000000005
RBP: 00000000007ff900 R08: 00007fc5ff9aa700 R09: 00007fc5ff9aa700
R10: 00007fc5ff9aa700 R11: 0000000000000246 R12: 0000000000000000
R13: 00000000007ff8ff R14: 00007fc5ff9aa9c0 R15: 0000000000000000
Allocated by task 15031:
save_stack+0x43/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3614
kmalloc include/linux/slab.h:516 [inline]
kzalloc include/linux/slab.h:705 [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:2992
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1530 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x1f/0x96
Freed by task 1402:
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+0x13c/0x1a0 arch/x86/kvm/../../../virt/kvm/eventfd.c:148
process_one_work+0xbfd/0x1bc0 kernel/workqueue.c:2113
worker_thread+0x223/0x1990 kernel/workqueue.c:2247
kthread+0x37a/0x440 kernel/kthread.c:238
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:524
The buggy address belongs to the object at ffff8801cdf51000
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 384 bytes inside of
512-byte region [ffff8801cdf51000, ffff8801cdf51200)
The buggy address belongs to the page:
page:00000000d08a0d63 count:1 mapcount:0 mapping:00000000d54c7be6 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cdf51000 0000000000000000 0000000100000006
raw: ffffea00073a7660 ffffea000737f3a0 ffff8801dac00940 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8801cdf51080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801cdf51100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801cdf51180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801cdf51200: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801cdf51280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
