KASAN: use-after-free Read in selinux_inode_free_security

[syzbot]

Hello,

syzbot hit the following crash on upstream commit
b89e32ccd1be92a3643df3908d3026b09e271616 (Fri Feb 2 21:46:21 2018 +0000)
Merge branch 'for-linus' of
git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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Reported-by: syzbot+145800...@syzkaller.appspotmail.com
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==================================================================
BUG: KASAN: use-after-free in list_empty_careful include/linux/list.h:221
[inline]
BUG: KASAN: use-after-free in inode_free_security
security/selinux/hooks.c:346 [inline]
BUG: KASAN: use-after-free in selinux_inode_free_security+0x3c1/0x410
security/selinux/hooks.c:2890
Read of size 8 at addr ffff8801d09b5488 by task syz-executor2/29672

CPU: 0 PID: 29672 Comm: syz-executor2 Not tainted 4.15.0+ #294
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_load8_noabort+0x14/0x20 mm/kasan/report.c:430
list_empty_careful include/linux/list.h:221 [inline]
inode_free_security security/selinux/hooks.c:346 [inline]
selinux_inode_free_security+0x3c1/0x410 security/selinux/hooks.c:2890
security_inode_free+0x50/0x90 security/security.c:443
__destroy_inode+0x287/0x660 fs/inode.c:237
destroy_inode+0xe7/0x200 fs/inode.c:264
evict+0x57e/0x920 fs/inode.c:571
iput_final fs/inode.c:1516 [inline]
iput+0x7b9/0xaf0 fs/inode.c:1543
dentry_unlink_inode+0x4b0/0x5e0 fs/dcache.c:371
d_delete+0x1ca/0x280 fs/dcache.c:2368
__debugfs_remove_file fs/debugfs/inode.c:626 [inline]
__debugfs_remove.part.10+0x185/0x250 fs/debugfs/inode.c:656
__debugfs_remove include/linux/dcache.h:492 [inline]
debugfs_remove_recursive+0x22e/0x5e0 fs/debugfs/inode.c:738
kvm_destroy_vm_debugfs arch/x86/kvm/../../../virt/kvm/kvm_main.c:562
[inline]
kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:716 [inline]
kvm_put_kvm+0x1da/0xde0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:756
kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:767
__fput+0x327/0x7e0 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x199/0x270 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x9bb/0x1ad0 kernel/exit.c:865
do_group_exit+0x149/0x400 kernel/exit.c:968
get_signal+0x73a/0x16d0 kernel/signal.c:2469
do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
exit_to_usermode_loop+0x258/0x2f0 arch/x86/entry/common.c:161
prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
entry_SYSCALL_64_fastpath+0x9e/0xa0
RIP: 0033:0x453299
RSP: 002b:00007f7f43691ce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000071bf80 RCX: 0000000000453299
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000071bf80
RBP: 000000000071bf80 R08: 000000000000060b R09: 000000000071bf58
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000a2f33f R14: 00007f7f436929c0 R15: 0000000000000002

Allocated by task 29664:
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
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
kmem_cache_alloc+0x12e/0x760 mm/slab.c:3540
kmem_cache_zalloc include/linux/slab.h:678 [inline]
inode_alloc_security security/selinux/hooks.c:234 [inline]
selinux_inode_alloc_security+0xf9/0x390 security/selinux/hooks.c:2885
security_inode_alloc+0x90/0xd0 security/security.c:437
inode_init_always+0x653/0xca0 fs/inode.c:168
alloc_inode+0x82/0x180 fs/inode.c:216
new_inode_pseudo+0x69/0x190 fs/inode.c:891
new_inode+0x1c/0x40 fs/inode.c:920
debugfs_get_inode+0x1b/0x120 fs/debugfs/inode.c:37
__debugfs_create_file+0x98/0x3d0 fs/debugfs/inode.c:355
debugfs_create_file+0x57/0x70 fs/debugfs/inode.c:402
kvm_create_vm_debugfs arch/x86/kvm/../../../virt/kvm/kvm_main.c:600
[inline]
kvm_dev_ioctl_create_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:3194
[inline]
kvm_dev_ioctl+0xbd4/0x18c0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3217
vfs_ioctl fs/ioctl.c:46 [inline]
do_vfs_ioctl+0x1b1/0x1520 fs/ioctl.c:686
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 29664:
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:3484 [inline]
kmem_cache_free+0x83/0x2a0 mm/slab.c:3742
inode_free_rcu+0x1d/0x20 security/selinux/hooks.c:328
__rcu_reclaim kernel/rcu/rcu.h:172 [inline]
rcu_do_batch kernel/rcu/tree.c:2674 [inline]
invoke_rcu_callbacks kernel/rcu/tree.c:2933 [inline]
__rcu_process_callbacks kernel/rcu/tree.c:2900 [inline]
rcu_process_callbacks+0xd6c/0x17f0 kernel/rcu/tree.c:2917
__do_softirq+0x2d7/0xb85 kernel/softirq.c:285

The buggy address belongs to the object at ffff8801d09b5480
which belongs to the cache selinux_inode_security of size 96
The buggy address is located 8 bytes inside of
96-byte region [ffff8801d09b5480, ffff8801d09b54e0)
The buggy address belongs to the page:
page:ffffea0007426d40 count:1 mapcount:0 mapping:ffff8801d09b5000
index:0xffff8801d09b5800
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801d09b5000 ffff8801d09b5800 000000010000001d
raw: ffffea00070743a0 ffffea0006c5c920 ffff8801da9c1240 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d09b5380: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
ffff8801d09b5400: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
> ffff8801d09b5480: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
^
ffff8801d09b5500: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
ffff8801d09b5580: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
==================================================================


---
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[Dmitry Vyukov]

On Wed, Feb 14, 2018 at 3:25 PM, syzbot
<syzbot+145800...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot hit the following crash on upstream commit
> b89e32ccd1be92a3643df3908d3026b09e271616 (Fri Feb 2 21:46:21 2018 +0000)
> Merge branch 'for-linus' of
> git://git.kernel.org/pub/scm/linux/kernel/git/mattst88/alpha
>
> Unfortunately, I don't have any reproducer for this crash yet.
> Raw console output is attached.
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached.

FTR, the previous bug about probably the same root cause:
https://groups.google.com/forum/#!msg/syzkaller-bugs/9JWqz8iHjuk/HLyjL4UAAgAJ

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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.