KASAN: use-after-free Read in kernel_accept

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    6bed5e260709 Merge branch 'fix-DCTCP-delayed-ACK'
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=176b25d0400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b88de6eac8694da6
dashboard link: https://syzkaller.appspot.com/bug?extid=0bf2e01269f1274b4b03
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=159dd178400000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13b76d62400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0bf2e01269f1274b4b03@xxxxxxxxxxxxxxxxxxxxxxxxx

==================================================================
BUG: KASAN: use-after-free in kernel_accept+0x2a4/0x310 net/socket.c:3251
Read of size 8 at addr ffff8801a772c5e8 by task kworker/1:3/4569

CPU: 1 PID: 4569 Comm: kworker/1:3 Not tainted 4.18.0-rc3+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events smc_tcp_listen_work
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 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_load8_noabort+0x14/0x20 mm/kasan/report.c:433
 kernel_accept+0x2a4/0x310 net/socket.c:3251
 smc_clcsock_accept net/smc/af_smc.c:701 [inline]
 smc_tcp_listen_work+0x222/0xef0 net/smc/af_smc.c:1114
 process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
 worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
 kthread+0x345/0x410 kernel/kthread.c:240
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Allocated by task 4568:
 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
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3554
 sock_alloc_inode+0x78/0x320 net/socket.c:243
 alloc_inode+0x63/0x190 fs/inode.c:210
 new_inode_pseudo+0x71/0x1a0 fs/inode.c:895
 sock_alloc+0x41/0x270 net/socket.c:567
 __sock_create+0x175/0x940 net/socket.c:1250
 sock_create_kern+0x3b/0x50 net/socket.c:1332
 smc_create+0x141/0x360 net/smc/af_smc.c:1701
 __sock_create+0x53c/0x940 net/socket.c:1286
 sock_create net/socket.c:1326 [inline]
 __sys_socket+0x106/0x260 net/socket.c:1356
 __do_sys_socket net/socket.c:1365 [inline]
 __se_sys_socket net/socket.c:1363 [inline]
 __x64_sys_socket+0x73/0xb0 net/socket.c:1363
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4568:
 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]
 kmem_cache_free+0x86/0x2d0 mm/slab.c:3756
 sock_destroy_inode+0x56/0x70 net/socket.c:273
 destroy_inode+0x159/0x200 fs/inode.c:267
 evict+0x5d5/0x990 fs/inode.c:575
 iput_final fs/inode.c:1506 [inline]
 iput+0x635/0xaa0 fs/inode.c:1532
 __sock_release+0x1f1/0x260 net/socket.c:610
 sock_release+0x17/0x20 net/socket.c:618
 smc_release+0x1a8/0x720 net/smc/af_smc.c:146
 __sock_release+0xd7/0x260 net/socket.c:599
 sock_close+0x19/0x20 net/socket.c:1150
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:192 [inline]
 exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801a772c5c0
 which belongs to the cache sock_inode_cache of size 992
The buggy address is located 40 bytes inside of
 992-byte region [ffff8801a772c5c0, ffff8801a772c9a0)
The buggy address belongs to the page:
page:ffffea00069dcb00 count:1 mapcount:0 mapping:ffff8801d9be93c0  
index:0xffff8801a772cffd
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffffea00069dcac8 ffffea00069dd408 ffff8801d9be93c0
raw: ffff8801a772cffd ffff8801a772c140 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801a772c480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8801a772c500: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
> ffff8801a772c580: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                          ^
 ffff8801a772c600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801a772c680: fb fb fb fb fb fb fb 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@xxxxxxxxxxxxxxxxx

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches