KASAN: use-after-free Read in get_disk

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b19ffe6e Linux 4.14.137
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1415e9ce600000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e8927aaaf4bd6e7
dashboard link: https://syzkaller.appspot.com/bug?extid=1128ee090b4b6823d0da
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+1128ee...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in get_disk+0xc9/0xe0 block/genhd.c:1433
Read of size 8 at addr ffff8880a0a411d0 by task blkid/11890

CPU: 0 PID: 11890 Comm: blkid Not tainted 4.14.137 #33
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+0x138/0x19c lib/dump_stack.c:53
print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
get_disk+0xc9/0xe0 block/genhd.c:1433
get_gendisk block/genhd.c:793 [inline]
get_gendisk+0xf5/0x240 block/genhd.c:778
__blkdev_get+0x3af/0x1120 fs/block_dev.c:1451
blkdev_get+0xa8/0x8e0 fs/block_dev.c:1612
blkdev_open+0x1d1/0x260 fs/block_dev.c:1770
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3425 [inline]
path_openat+0x8bd/0x3f70 fs/namei.c:3566
do_filp_open+0x18e/0x250 fs/namei.c:3600
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_open fs/open.c:1102 [inline]
SyS_open+0x2d/0x40 fs/open.c:1097
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x7f0bf02a1120
RSP: 002b:00007ffd706f8708 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f0bf02a1120
RDX: 00007ffd706f9f18 RSI: 0000000000000000 RDI: 00007ffd706f9f18
RBP: 0000000000000000 R08: 0000000000000078 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000001eda030
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000005

Allocated by task 11866:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
kmem_cache_alloc_node_trace+0x153/0x770 mm/slab.c:3661
kmalloc_node include/linux/slab.h:526 [inline]
kzalloc_node include/linux/slab.h:672 [inline]
alloc_disk_node+0x64/0x3e0 block/genhd.c:1387
alloc_disk+0x1b/0x20 block/genhd.c:1371
loop_add+0x3e7/0x850 drivers/block/loop.c:1858
loop_control_ioctl+0x10c/0x2f0 drivers/block/loop.c:1990
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:500 [inline]
do_vfs_ioctl+0x7ae/0x1060 fs/ioctl.c:684
SYSC_ioctl fs/ioctl.c:701 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:692
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

Freed by task 11888:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcc/0x270 mm/slab.c:3815
disk_release+0x24b/0x2d0 block/genhd.c:1230
device_release+0xf6/0x1a0 drivers/base/core.c:822
kobject_cleanup lib/kobject.c:646 [inline]
kobject_release lib/kobject.c:675 [inline]
kref_put include/linux/kref.h:70 [inline]
kobject_put.cold+0x269/0x2f9 lib/kobject.c:692
put_disk+0x23/0x30 block/genhd.c:1452
__blkdev_get+0x6a6/0x1120 fs/block_dev.c:1570
blkdev_get+0xa8/0x8e0 fs/block_dev.c:1612
blkdev_open+0x1d1/0x260 fs/block_dev.c:1770
do_dentry_open+0x73b/0xeb0 fs/open.c:777
vfs_open+0x105/0x220 fs/open.c:891
do_last fs/namei.c:3425 [inline]
path_openat+0x8bd/0x3f70 fs/namei.c:3566
do_filp_open+0x18e/0x250 fs/namei.c:3600
do_sys_open+0x2c5/0x430 fs/open.c:1084
SYSC_open fs/open.c:1102 [inline]
SyS_open+0x2d/0x40 fs/open.c:1097
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7

The buggy address belongs to the object at ffff8880a0a40c80
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 1360 bytes inside of
2048-byte region [ffff8880a0a40c80, ffff8880a0a41480)
The buggy address belongs to the page:
page:ffffea0002829000 count:1 mapcount:0 mapping:ffff8880a0a40400 index:0x0
compound_mapcount: 0
flags: 0x1fffc0000008100(slab|head)
raw: 01fffc0000008100 ffff8880a0a40400 0000000000000000 0000000100000003
raw: ffffea00022a8ea0 ffffea00023837a0 ffff8880aa800c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a0a41080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a0a41100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8880a0a41180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880a0a41200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880a0a41280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


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[syzbot]

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