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SubjectKASAN: use-after-free Read in x25_device_event
From
Hello,

syzbot found the following crash on:

HEAD commit: 38355a5f9a22 bnx2x: Fix NULL pointer dereference in bnx2x_..
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=144e49ed400000
kernel config: https://syzkaller.appspot.com/x/.config?x=7321a72d3309c029
dashboard link: https://syzkaller.appspot.com/bug?extid=04babcefcd396fabec37
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+04babcefcd396fabec37@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in x25_kill_by_device net/x25/af_x25.c:217
[inline]
BUG: KASAN: use-after-free in x25_device_event+0x297/0x2b0
net/x25/af_x25.c:252
Read of size 8 at addr ffff8881b5c85ad0 by task syz-executor2/22350

CPU: 1 PID: 22350 Comm: syz-executor2 Not tainted 4.20.0-rc7+ #248
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+0x1d3/0x2c6 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
x25_kill_by_device net/x25/af_x25.c:217 [inline]
x25_device_event+0x297/0x2b0 net/x25/af_x25.c:252
notifier_call_chain+0x17e/0x380 kernel/notifier.c:93
__raw_notifier_call_chain kernel/notifier.c:394 [inline]
raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1733
call_netdevice_notifiers net/core/dev.c:1751 [inline]
__dev_notify_flags+0x29b/0x480 net/core/dev.c:7547
dev_change_flags+0xfd/0x150 net/core/dev.c:7581
dev_ifsioc+0x7d6/0xa80 net/core/dev_ioctl.c:237
dev_ioctl+0x1b5/0xcc0 net/core/dev_ioctl.c:488
sock_do_ioctl+0x1f6/0x420 net/socket.c:973
sock_ioctl+0x313/0x690 net/socket.c:1074
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457759
Code: fd b3 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 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f4c06d4fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457759
RDX: 00000000200005c0 RSI: 0000000000008914 RDI: 0000000000000005
RBP: 000000000073bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f4c06d506d4
R13: 00000000004c2c32 R14: 00000000004d52f8 R15: 00000000ffffffff

Allocated by task 10606:
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
kmem_cache_alloc_trace+0x152/0x750 mm/slab.c:3620
kmalloc include/linux/slab.h:546 [inline]
x25_link_device_up+0xb2/0x500 net/x25/x25_link.c:249
x25_device_event+0x116/0x2b0 net/x25/af_x25.c:242
notifier_call_chain+0x17e/0x380 kernel/notifier.c:93
__raw_notifier_call_chain kernel/notifier.c:394 [inline]
raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1733
call_netdevice_notifiers net/core/dev.c:1751 [inline]
__dev_notify_flags+0x17a/0x480 net/core/dev.c:7545
dev_change_flags+0xfd/0x150 net/core/dev.c:7581
dev_ifsioc+0x7d6/0xa80 net/core/dev_ioctl.c:237
dev_ioctl+0x1b5/0xcc0 net/core/dev_ioctl.c:488
sock_do_ioctl+0x1f6/0x420 net/socket.c:973
sock_ioctl+0x313/0x690 net/socket.c:1074
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 22299:
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]
kfree+0xcf/0x230 mm/slab.c:3817
x25_neigh_put include/net/x25.h:253 [inline]
__x25_remove_neigh+0x233/0x310 net/x25/x25_link.c:290
x25_link_device_down+0xc7/0x130 net/x25/x25_link.c:308
x25_device_event+0x262/0x2b0 net/x25/af_x25.c:254
notifier_call_chain+0x17e/0x380 kernel/notifier.c:93
__raw_notifier_call_chain kernel/notifier.c:394 [inline]
raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
call_netdevice_notifiers_info+0x3f/0x90 net/core/dev.c:1733
call_netdevice_notifiers net/core/dev.c:1751 [inline]
__dev_notify_flags+0x29b/0x480 net/core/dev.c:7547
dev_change_flags+0xfd/0x150 net/core/dev.c:7581
dev_ifsioc+0x7d6/0xa80 net/core/dev_ioctl.c:237
dev_ioctl+0x1b5/0xcc0 net/core/dev_ioctl.c:488
sock_do_ioctl+0x1f6/0x420 net/socket.c:973
sock_ioctl+0x313/0x690 net/socket.c:1074
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:509 [inline]
do_vfs_ioctl+0x1de/0x1790 fs/ioctl.c:696
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:713
__do_sys_ioctl fs/ioctl.c:720 [inline]
__se_sys_ioctl fs/ioctl.c:718 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:718
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 ffff8881b5c85ac0
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 16 bytes inside of
256-byte region [ffff8881b5c85ac0, ffff8881b5c85bc0)
The buggy address belongs to the page:
page:ffffea0006d72140 count:1 mapcount:0 mapping:ffff8881da8007c0
index:0xffff8881b5c85e80
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea00075f33c8 ffffea000731be48 ffff8881da8007c0
raw: ffff8881b5c85e80 ffff8881b5c850c0 0000000100000008 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8881b5c85980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881b5c85a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881b5c85a80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
^
ffff8881b5c85b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8881b5c85b80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================


---
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.

syzbot will keep track of this bug report. See:
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syzbot.

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