KASAN: use-after-free Read in inet_shutdown

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2c8a3fce Linux 4.14.218
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=154fefc2d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=80e596b8b0902d96
dashboard link: https://syzkaller.appspot.com/bug?extid=a8164ec9499221ceaa73

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a8164e...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in inet_shutdown+0x2c0/0x340 syzkaller/managers/linux-4-14/kernel/net/ipv4/af_inet.c:816
Read of size 4 at addr ffff88804db43b00 by task syz-executor.0/15428

CPU: 1 PID: 15428 Comm: syz-executor.0 Not tainted 4.14.218-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 syzkaller/managers/linux-4-14/kernel/mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x191 syzkaller/managers/linux-4-14/kernel/mm/kasan/report.c:351
kasan_report syzkaller/managers/linux-4-14/kernel/mm/kasan/report.c:409 [inline]
__asan_report_load4_noabort+0x68/0x70 syzkaller/managers/linux-4-14/kernel/mm/kasan/report.c:429
inet_shutdown+0x2c0/0x340 syzkaller/managers/linux-4-14/kernel/net/ipv4/af_inet.c:816
pppol2tp_session_close+0x8f/0xe0 syzkaller/managers/linux-4-14/kernel/net/l2tp/l2tp_ppp.c:449
l2tp_tunnel_closeall+0x235/0x370 syzkaller/managers/linux-4-14/kernel/net/l2tp/l2tp_core.c:1347
l2tp_udp_encap_destroy+0x8d/0xf0 syzkaller/managers/linux-4-14/kernel/net/l2tp/l2tp_core.c:1373
udpv6_destroy_sock+0xef/0x190 syzkaller/managers/linux-4-14/kernel/net/ipv6/udp.c:1444
sk_common_release+0x64/0x2c0 syzkaller/managers/linux-4-14/kernel/net/core/sock.c:3015
inet_release+0xdf/0x1b0 syzkaller/managers/linux-4-14/kernel/net/ipv4/af_inet.c:425
inet6_release+0x4c/0x70 syzkaller/managers/linux-4-14/kernel/net/ipv6/af_inet6.c:450
__sock_release+0xcd/0x2b0 syzkaller/managers/linux-4-14/kernel/net/socket.c:602
sock_close+0x15/0x20 syzkaller/managers/linux-4-14/kernel/net/socket.c:1139
__fput+0x25f/0x7a0 syzkaller/managers/linux-4-14/kernel/fs/file_table.c:210
task_work_run+0x11f/0x190 syzkaller/managers/linux-4-14/kernel/kernel/task_work.c:113
tracehook_notify_resume syzkaller/managers/linux-4-14/kernel/./include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:164
prepare_exit_to_usermode syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x4190ab
RSP: 002b:00007fff5eb00ea0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: 0000000000000000 RBX: 0000000000000006 RCX: 00000000004190ab
RDX: ffffffff86fd452b RSI: 0000001b2e02c850 RDI: 0000000000000005
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000001b2f020000
R10: 0018d592261417e0 R11: 0000000000000293 R12: 000000000056c9e0
R13: 00000000000416df R14: 000000000056c9e0 R15: 000000000056c008

Allocated by task 15431:
save_stack syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:447 [inline]
set_track syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xeb/0x160 syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:551
kmem_cache_alloc+0x124/0x3c0 syzkaller/managers/linux-4-14/kernel/mm/slab.c:3552
sock_alloc_inode+0x19/0x250 syzkaller/managers/linux-4-14/kernel/net/socket.c:251
alloc_inode+0x5d/0x170 syzkaller/managers/linux-4-14/kernel/fs/inode.c:210
new_inode_pseudo+0x14/0xe0 syzkaller/managers/linux-4-14/kernel/fs/inode.c:899
sock_alloc+0x3c/0x270 syzkaller/managers/linux-4-14/kernel/net/socket.c:569
__sock_create+0x8a/0x620 syzkaller/managers/linux-4-14/kernel/net/socket.c:1239
sock_create syzkaller/managers/linux-4-14/kernel/net/socket.c:1315 [inline]
SYSC_socket syzkaller/managers/linux-4-14/kernel/net/socket.c:1345 [inline]
SyS_socket+0xd1/0x1b0 syzkaller/managers/linux-4-14/kernel/net/socket.c:1325
do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 15431:
save_stack syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:447 [inline]
set_track syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xc3/0x1a0 syzkaller/managers/linux-4-14/kernel/mm/kasan/kasan.c:524
__cache_free syzkaller/managers/linux-4-14/kernel/mm/slab.c:3496 [inline]
kmem_cache_free+0x7c/0x2b0 syzkaller/managers/linux-4-14/kernel/mm/slab.c:3758
destroy_inode+0xb9/0x110 syzkaller/managers/linux-4-14/kernel/fs/inode.c:267
iput_final syzkaller/managers/linux-4-14/kernel/fs/inode.c:1524 [inline]
iput+0x458/0x7e0 syzkaller/managers/linux-4-14/kernel/fs/inode.c:1551
dentry_unlink_inode+0x25c/0x310 syzkaller/managers/linux-4-14/kernel/fs/dcache.c:387
__dentry_kill+0x320/0x550 syzkaller/managers/linux-4-14/kernel/fs/dcache.c:591
dentry_kill syzkaller/managers/linux-4-14/kernel/fs/dcache.c:632 [inline]
dput.part.0+0x56f/0x710 syzkaller/managers/linux-4-14/kernel/fs/dcache.c:847
dput+0x1b/0x30 syzkaller/managers/linux-4-14/kernel/fs/dcache.c:811
__fput+0x445/0x7a0 syzkaller/managers/linux-4-14/kernel/fs/file_table.c:228
task_work_run+0x11f/0x190 syzkaller/managers/linux-4-14/kernel/kernel/task_work.c:113
tracehook_notify_resume syzkaller/managers/linux-4-14/kernel/./include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:164
prepare_exit_to_usermode syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88804db43b00
which belongs to the cache sock_inode_cache of size 1000
The buggy address is located 0 bytes inside of
1000-byte region [ffff88804db43b00, ffff88804db43ee8)
The buggy address belongs to the page:
page:ffffea000136d0c0 count:1 mapcount:0 mapping:ffff88804db43200 index:0xffff88804db43ffd
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff88804db43200 ffff88804db43ffd 0000000100000003
raw: ffffea000136d4e0 ffffea000136b6a0 ffff8880b5532900 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88804db43a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
ffff88804db43a80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88804db43b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88804db43b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88804db43c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report 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 syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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