KASAN: use-after-free Read in pipe_wait

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 3a979e8c07e3 Merge tag 'mailbox-v4.18' of git://git.linaro..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1149756f800000
kernel config: https://syzkaller.appspot.com/x/.config?x=412e35656a3f7c09
dashboard link: https://syzkaller.appspot.com/bug?extid=da0d8da4d4013230042d
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org
vi...@zeniv.linux.org.uk]

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+da0d8d...@syzkaller.appspotmail.com

bpfilter: read fail -512
==================================================================
BUG: KASAN: use-after-free in pipe_lock_nested fs/pipe.c:61 [inline]
BUG: KASAN: use-after-free in pipe_lock fs/pipe.c:70 [inline]
BUG: KASAN: use-after-free in pipe_wait+0x251/0x2a0 fs/pipe.c:118
Read of size 4 at addr ffff8801cda4885c by task syz-executor3/4576

CPU: 1 PID: 4576 Comm: syz-executor3 Not tainted 4.17.0+ #83
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+0x1b9/0x294 lib/dump_stack.c:113
print_address_description+0x6c/0x20b mm/kasan/report.c:256
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
pipe_lock_nested fs/pipe.c:61 [inline]
pipe_lock fs/pipe.c:70 [inline]
pipe_wait+0x251/0x2a0 fs/pipe.c:118
pipe_read+0x37c/0x940 fs/pipe.c:333
call_read_iter include/linux/fs.h:1785 [inline]
new_sync_read fs/read_write.c:406 [inline]
__vfs_read+0x696/0xa50 fs/read_write.c:418
IPVS: ftp: loaded support on port[0] = 21
vfs_read+0x17f/0x3d0 fs/read_write.c:452
kernel_read+0xab/0x120 fs/read_write.c:431
__bpfilter_process_sockopt+0x238/0x35b net/bpfilter/bpfilter_kern.c:74
bpfilter_mbox_request+0x4d/0xb0 net/ipv4/bpfilter/sockopt.c:25
bpfilter_ip_get_sockopt+0x6b/0x90 net/ipv4/bpfilter/sockopt.c:42
ip_getsockopt+0x238/0x2a0 net/ipv4/ip_sockglue.c:1563
tcp_getsockopt+0x93/0xe0 net/ipv4/tcp.c:3532
sock_common_getsockopt+0x9a/0xe0 net/core/sock.c:3012
__sys_getsockopt+0x1a5/0x370 net/socket.c:1972
__do_sys_getsockopt net/socket.c:1983 [inline]
__se_sys_getsockopt net/socket.c:1980 [inline]
__x64_sys_getsockopt+0xbe/0x150 net/socket.c:1980
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4584ea
Code: b8 34 01 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 1d 8f fb ff c3 66 2e 0f
1f 84 00 00 00 00 00 66 90 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 01 f0 ff
ff 0f 83 fa 8e fb ff c3 66 0f 1f 84 00 00 00 00 00
RSP: 002b:0000000000a3e328 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000a3e350 RCX: 00000000004584ea
RDX: 0000000000000040 RSI: 0000000000000000 RDI: 0000000000000013
RBP: 0000000000706f20 R08: 0000000000a3e34c R09: 0000000000004000
R10: 0000000000a3e350 R11: 0000000000000246 R12: 0000000000000013
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000704d60

Allocated by task 2224:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620
kmalloc include/linux/slab.h:513 [inline]
kzalloc include/linux/slab.h:706 [inline]
alloc_pipe_info+0x16d/0x580 fs/pipe.c:636
get_pipe_inode fs/pipe.c:715 [inline]
create_pipe_files+0xd0/0x940 fs/pipe.c:748
umh_pipe_setup+0x17b/0x430 kernel/umh.c:442
call_usermodehelper_exec_async+0x3c0/0x9e0 kernel/umh.c:93
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Freed by task 2224:
save_stack+0x43/0xd0 mm/kasan/kasan.c:448
set_track mm/kasan/kasan.c:460 [inline]
__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
__cache_free mm/slab.c:3498 [inline]
kfree+0xd9/0x260 mm/slab.c:3813
free_pipe_info+0x253/0x300 fs/pipe.c:687
put_pipe_info+0xd0/0xf0 fs/pipe.c:559
pipe_release+0x1de/0x270 fs/pipe.c:580
__fput+0x353/0x890 fs/file_table.c:209
____fput+0x15/0x20 fs/file_table.c:243
task_work_run+0x1e4/0x290 kernel/task_work.c:113
exit_task_work include/linux/task_work.h:22 [inline]
do_exit+0x1aee/0x2730 kernel/exit.c:865
do_group_exit+0x16f/0x430 kernel/exit.c:968
__do_sys_exit_group kernel/exit.c:979 [inline]
__se_sys_exit_group kernel/exit.c:977 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:977
do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801cda48780
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 220 bytes inside of
512-byte region [ffff8801cda48780, ffff8801cda48980)
The buggy address belongs to the page:
page:ffffea0007369200 count:1 mapcount:0 mapping:ffff8801cda48000 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cda48000 0000000000000000 0000000100000006
raw: ffffea00075f3360 ffffea000750d320 ffff8801da800940 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801cda48700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801cda48780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801cda48800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801cda48880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801cda48900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Dmitry Vyukov]

#syz fix: bpfilter: fix race in pipe access

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