KASAN: use-after-free Read in inet_shutdown (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cd5296934610 Linux 4.14.253
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13390204b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=62a045ef49739704
dashboard link: https://syzkaller.appspot.com/bug?extid=45a4b8bca520f5366e2a
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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+45a4b8...@syzkaller.appspotmail.com

audit: type=1804 audit(1635375330.626:5): pid=9424 uid=0 auid=4294967295 ses=4294967295 op="invalid_pcr" cause="open_writers" comm="syz-executor.0" name="/root/syzkaller-testdir178465045/syzkaller.19hTpj/0/file0/bus" dev="loop0" ino=7 res=1
==================================================================
BUG: KASAN: use-after-free in inet_shutdown+0x2c0/0x340 net/ipv4/af_inet.c:816
Read of size 4 at addr ffff88805849fb00 by task kworker/u4:4/3551

CPU: 0 PID: 3551 Comm: kworker/u4:4 Not tainted 4.14.253-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: l2tp l2tp_tunnel_del_work
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x1b2/0x281 lib/dump_stack.c:58
print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
kasan_report_error.cold+0x8a/0x191 mm/kasan/report.c:351
kasan_report mm/kasan/report.c:409 [inline]
__asan_report_load4_noabort+0x68/0x70 mm/kasan/report.c:429
inet_shutdown+0x2c0/0x340 net/ipv4/af_inet.c:816
pppol2tp_session_close+0x8f/0xe0 net/l2tp/l2tp_ppp.c:449
l2tp_tunnel_closeall+0x235/0x370 net/l2tp/l2tp_core.c:1349
l2tp_tunnel_del_work+0x62/0x400 net/l2tp/l2tp_core.c:1389
process_one_work+0x793/0x14a0 kernel/workqueue.c:2117
worker_thread+0x5cc/0xff0 kernel/workqueue.c:2251
kthread+0x30d/0x420 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 9484:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
kmem_cache_alloc+0x124/0x3c0 mm/slab.c:3552
sock_alloc_inode+0x19/0x250 net/socket.c:251
alloc_inode+0x5d/0x170 fs/inode.c:210
new_inode_pseudo+0x14/0xe0 fs/inode.c:899
sock_alloc+0x3c/0x270 net/socket.c:569
__sock_create+0x8a/0x620 net/socket.c:1239
sock_create net/socket.c:1315 [inline]
SYSC_socket net/socket.c:1345 [inline]
SyS_socket+0xd1/0x1b0 net/socket.c:1325
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 9483:
save_stack mm/kasan/kasan.c:447 [inline]
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kmem_cache_free+0x7c/0x2b0 mm/slab.c:3758
destroy_inode+0xb9/0x110 fs/inode.c:267
iput_final fs/inode.c:1524 [inline]
iput+0x458/0x7e0 fs/inode.c:1551
dentry_unlink_inode+0x25c/0x310 fs/dcache.c:387
__dentry_kill+0x320/0x550 fs/dcache.c:591
dentry_kill fs/dcache.c:632 [inline]
dput.part.0+0x56f/0x710 fs/dcache.c:847
dput+0x1b/0x30 fs/dcache.c:811
__fput+0x445/0x7a0 fs/file_table.c:228
task_work_run+0x11f/0x190 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:191 [inline]
exit_to_usermode_loop+0x1ad/0x200 arch/x86/entry/common.c:164
prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
do_syscall_64+0x4a3/0x640 arch/x86/entry/common.c:297
entry_SYSCALL_64_after_hwframe+0x46/0xbb

The buggy address belongs to the object at ffff88805849fb00
which belongs to the cache sock_inode_cache of size 1000
The buggy address is located 0 bytes inside of
1000-byte region [ffff88805849fb00, ffff88805849fee8)
The buggy address belongs to the page:
page:ffffea00016127c0 count:1 mapcount:0 mapping:ffff88805849f200 index:0xffff88805849fffd
flags: 0xfff00000000100(slab)
raw: 00fff00000000100 ffff88805849f200 ffff88805849fffd 0000000100000003
raw: ffffea0001612760 ffffea0001612820 ffff8880b5f936c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88805849fa00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
ffff88805849fa80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88805849fb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88805849fb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88805849fc00: 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.