linux-kernel - KASAN: use-after-free Write in start

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Date:   Sun, 07 Jun 2020 02:10:17 -0700
From:   syzbot <syzbot+ee19362d7c0417910752@...kaller.appspotmail.com>
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        rafael@...nel.org, syzkaller-bugs@...glegroups.com
Subject: KASAN: use-after-free Write in start_creating

Hello,

syzbot found the following crash on:

HEAD commit:    7ae77150 Merge tag 'powerpc-5.8-1' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1441c9de100000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d195fe572fb15312
dashboard link: https://syzkaller.appspot.com/bug?extid=ee19362d7c0417910752
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+ee19362d7c0417910752@...kaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in atomic64_set include/asm-generic/atomic-instrumented.h:854 [inline]
BUG: KASAN: use-after-free in atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
BUG: KASAN: use-after-free in rwsem_set_owner kernel/locking/rwsem.c:176 [inline]
BUG: KASAN: use-after-free in __down_write kernel/locking/rwsem.c:1391 [inline]
BUG: KASAN: use-after-free in down_write+0xdb/0x150 kernel/locking/rwsem.c:1532
Write of size 8 at addr ffff8880277496e8 by task syz-executor.3/17503

CPU: 1 PID: 17503 Comm: syz-executor.3 Not tainted 5.7.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x413 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x141/0x190 mm/kasan/generic.c:192
 atomic64_set include/asm-generic/atomic-instrumented.h:854 [inline]
 atomic_long_set include/asm-generic/atomic-long.h:40 [inline]
 rwsem_set_owner kernel/locking/rwsem.c:176 [inline]
 __down_write kernel/locking/rwsem.c:1391 [inline]
 down_write+0xdb/0x150 kernel/locking/rwsem.c:1532
 inode_lock include/linux/fs.h:799 [inline]
 start_creating+0xa8/0x250 fs/debugfs/inode.c:334
 __debugfs_create_file+0x62/0x400 fs/debugfs/inode.c:383
 kvm_arch_create_vcpu_debugfs+0x52/0x200 arch/x86/kvm/debugfs.c:48
 kvm_create_vcpu_debugfs arch/x86/kvm/../../../virt/kvm/kvm_main.c:3012 [inline]
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3089 [inline]
 kvm_vm_ioctl+0x1c0b/0x2440 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3617
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:771
 __do_sys_ioctl fs/ioctl.c:780 [inline]
 __se_sys_ioctl fs/ioctl.c:778 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:778
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45ca69
Code: 0d b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 db b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f40f5451c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00000000004e7400 RCX: 000000000045ca69
RDX: 0000000000000000 RSI: 000000000000ae41 RDI: 0000000000000005
RBP: 000000000078bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 0000000000000396 R14: 00000000004c6306 R15: 00007f40f54526d4

Allocated by task 17503:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc mm/kasan/common.c:494 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:467
 slab_post_alloc_hook mm/slab.h:586 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc+0x11b/0x740 mm/slab.c:3484
 alloc_inode+0x164/0x1e0 fs/inode.c:234
 new_inode_pseudo+0x14/0xe0 fs/inode.c:928
 new_inode+0x1b/0x40 fs/inode.c:957
 debugfs_get_inode+0x1a/0x130 fs/debugfs/inode.c:67
 debugfs_create_dir+0x71/0x390 fs/debugfs/inode.c:544
 kvm_create_vcpu_debugfs arch/x86/kvm/../../../virt/kvm/kvm_main.c:3009 [inline]
 kvm_vm_ioctl_create_vcpu arch/x86/kvm/../../../virt/kvm/kvm_main.c:3089 [inline]
 kvm_vm_ioctl+0x1bd8/0x2440 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3617
 vfs_ioctl fs/ioctl.c:47 [inline]
 ksys_ioctl+0x11a/0x180 fs/ioctl.c:771
 __do_sys_ioctl fs/ioctl.c:780 [inline]
 __se_sys_ioctl fs/ioctl.c:778 [inline]
 __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:778
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 2478:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kmem_cache_free+0x7f/0x320 mm/slab.c:3694
 i_callback+0x3f/0x70 fs/inode.c:221
 rcu_do_batch kernel/rcu/tree.c:2396 [inline]
 rcu_core+0x59f/0x1370 kernel/rcu/tree.c:2623
 __do_softirq+0x26c/0x9f7 kernel/softirq.c:292

The buggy address belongs to the object at ffff888027749600
 which belongs to the cache inode_cache of size 1024
The buggy address is located 232 bytes inside of
 1024-byte region [ffff888027749600, ffff888027749a00)
The buggy address belongs to the page:
page:ffffea00009dd240 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888027749ffd
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0001412e48 ffffea00009db2c8 ffff8880aa201380
raw: ffff888027749ffd ffff888027749180 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888027749580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888027749600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888027749680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                          ^
 ffff888027749700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888027749780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
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