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SubjectKASAN: use-after-free Read in do_exit
From
Hello,

syzbot found the following crash on:

HEAD commit: 58a022870787 Merge tag 'acpi-4.20-rc1' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12a0f939400000
kernel config: https://syzkaller.appspot.com/x/.config?x=414a8e66ba2c6789
dashboard link: https://syzkaller.appspot.com/bug?extid=71a06dcf7e167c30ab9d
compiler: gcc (GCC) 8.0.1 20180413 (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+71a06dcf7e167c30ab9d@syzkaller.appspotmail.com

TCP: request_sock_TCPv6: Possible SYN flooding on port 20002. Sending
cookies. Check SNMP counters.
input: syz1 as /devices/virtual/input/input1084
netlink: 20 bytes leftover after parsing attributes in process
`syz-executor2'.
kasan: CONFIG_KASAN_INLINE enabled
==================================================================
BUG: KASAN: use-after-free in stack_not_used
include/linux/sched/task_stack.h:101 [inline]
BUG: KASAN: use-after-free in check_stack_usage kernel/exit.c:748 [inline]
BUG: KASAN: use-after-free in do_exit+0x2196/0x26d0 kernel/exit.c:916
Read of size 8 at addr ffff8801c2b90008 by task blkid/5862

CPU: 1 PID: 5862 Comm: blkid Not tainted 4.19.0+ #299
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+0x1c4/0x2b6 lib/dump_stack.c:113
print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
stack_not_used include/linux/sched/task_stack.h:101 [inline]
check_stack_usage kernel/exit.c:748 [inline]
do_exit+0x2196/0x26d0 kernel/exit.c:916
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 0 PID: 5797 Comm: syz-executor4 Not tainted 4.19.0+ #299
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
RIP: 0010:compound_head include/linux/page-flags.h:142 [inline]
RIP: 0010:put_page include/linux/mm.h:931 [inline]
RIP: 0010:tls_sk_proto_close+0x419/0xbb0 net/tls/tls_main.c:277
Code: 8d e8 fe ff ff 48 89 85 f0 fe ff ff e8 b0 55 db fa 48 8b 85 f0 fe ff
ff 49 83 e5 fc 49 8d 7d 08 c6 00 00 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00
0f 85 ad 06 00 00 48 8b 85 f0 fe ff ff 4d 8b 75 08
RSP: 0018:ffff88018c2e6f70 EFLAGS: 00010202
RAX: 0000000000000001 RBX: ffff88018566ae40 RCX: ffffffff86a36050
RDX: 0000000000000000 RSI: ffffffff86a35e10 RDI: 0000000000000008
RBP: ffff88018c2e70d0 R08: ffff880182d0c580 R09: 0000000000000006
R10: 0000000000000000 R11: ffff880182d0c580 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: ffff88018ba82740
FS: 00007f2e39ea9700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b32334000 CR3: 00000001ccbdb000 CR4: 00000000001426f0
Call Trace:
inet_release+0x104/0x1f0 net/ipv4/af_inet.c:428
inet6_release+0x50/0x70 net/ipv6/af_inet6.c:457
__sock_release+0xd7/0x250 net/socket.c:579
sock_close+0x19/0x20 net/socket.c:1141
__fput+0x385/0xa30 fs/file_table.c:278
do_group_exit+0x177/0x440 kernel/exit.c:970
____fput+0x15/0x20 fs/file_table.c:309
task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
__do_sys_exit_group kernel/exit.c:981 [inline]
__se_sys_exit_group kernel/exit.c:979 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x1ad6/0x26d0 kernel/exit.c:867
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f564809d1e8
Code: Bad RIP value.
RSP: 002b:00007ffd77478cc8 EFLAGS: 00000246
ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f564809d1e8
RDX: 0000000000000002 RSI: 000000000000003c RDI: 0000000000000002
RBP: 00007f5648372840 R08: 00000000000000e7 R09: ffffffffffffffa8
R10: 00007f5648378740 R11: 0000000000000246 R12: 00007f5648372840
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 5279:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
kmem_cache_zalloc include/linux/slab.h:697 [inline]
locks_alloc_lock+0x8e/0x270 fs/locks.c:303
fcntl_setlk+0xc8/0xfb0 fs/locks.c:2246
do_fcntl+0xa6f/0x1500 fs/fcntl.c:370
__do_sys_fcntl fs/fcntl.c:463 [inline]
__se_sys_fcntl fs/fcntl.c:448 [inline]
__x64_sys_fcntl+0x177/0x1f0 fs/fcntl.c:448
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 5279:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kmem_cache_free+0x83/0x290 mm/slab.c:3756
locks_free_lock+0x209/0x340 fs/locks.c:339
fcntl_setlk+0x79f/0xfb0 fs/locks.c:2323
do_fcntl+0xa6f/0x1500 fs/fcntl.c:370
__do_sys_fcntl fs/fcntl.c:463 [inline]
__se_sys_fcntl fs/fcntl.c:448 [inline]
__x64_sys_fcntl+0x177/0x1f0 fs/fcntl.c:448
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801c2b90000
which belongs to the cache file_lock_cache of size 248
The buggy address is located 8 bytes inside of
248-byte region [ffff8801c2b90000, ffff8801c2b900f8)
The buggy address belongs to the page:
do_group_exit+0x177/0x440 kernel/exit.c:970
page:ffffea00070ae400 count:1 mapcount:0 mapping:ffff8801d9bf5b00 index:0x0
get_signal+0x8b0/0x1980 kernel/signal.c:2513
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea000709e388 ffffea0006039548 ffff8801d9bf5b00
raw: 0000000000000000 ffff8801c2b90000 000000010000000d 0000000000000000
page dumped because: kasan: bad access detected
do_signal+0x9c/0x21e0 arch/x86/kernel/signal.c:816

Memory state around the buggy address:
ffff8801c2b8ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801c2b8ff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ffff8801c2b90000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801c2b90080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc
ffff8801c2b90100: fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

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syzbot.

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