KASAN: use-after-free Read in l2cap_sock_kill

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 015e94d0 Linux 4.19.146
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1162929b900000
kernel config: https://syzkaller.appspot.com/x/.config?x=56a448674cefaa8a
dashboard link: https://syzkaller.appspot.com/bug?extid=b673a563b3a339728b15
compiler: gcc (GCC) 10.1.0-syz 20200507

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+b673a5...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in constant_test_bit arch/x86/include/asm/bitops.h:317 [inline]
BUG: KASAN: use-after-free in sock_flag include/net/sock.h:839 [inline]
BUG: KASAN: use-after-free in l2cap_sock_kill+0xdb/0x100 net/bluetooth/l2cap_sock.c:1046
Read of size 8 at addr ffff88808733ef20 by task syz-executor.3/27368

CPU: 0 PID: 27368 Comm: syz-executor.3 Not tainted 4.19.146-syzkaller #0
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+0x22c/0x33e lib/dump_stack.c:118
print_address_description.cold+0x56/0x25c mm/kasan/report.c:256
kasan_report_error.cold+0x66/0xb9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
constant_test_bit arch/x86/include/asm/bitops.h:317 [inline]
sock_flag include/net/sock.h:839 [inline]
l2cap_sock_kill+0xdb/0x100 net/bluetooth/l2cap_sock.c:1046
l2cap_conn_del+0x3db/0x6b0 net/bluetooth/l2cap_core.c:1730
l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7435 [inline]
l2cap_disconn_cfm+0x85/0xa0 net/bluetooth/l2cap_core.c:7428
hci_disconn_cfm include/net/bluetooth/hci_core.h:1261 [inline]
hci_conn_hash_flush+0x114/0x220 net/bluetooth/hci_conn.c:1495
hci_dev_do_close+0x623/0xe70 net/bluetooth/hci_core.c:1666
hci_rfkill_set_block+0x102/0x130 net/bluetooth/hci_core.c:2100
rfkill_set_block+0x1f9/0x4b0 net/rfkill/core.c:353
rfkill_fop_write+0x287/0x580 net/rfkill/core.c:1249
__vfs_write+0xf7/0x770 fs/read_write.c:485
vfs_write+0x1f3/0x540 fs/read_write.c:549
ksys_write+0x12b/0x2a0 fs/read_write.c:599
do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x45d5f9
Code: 5d b4 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 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f2a44a0dc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000039280 RCX: 000000000045d5f9
RDX: 0000000000000008 RSI: 0000000020000040 RDI: 0000000000000003
RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c
R13: 00007ffd1d4b4a1f R14: 00007f2a44a0e9c0 R15: 000000000118cf4c

Allocated by task 27378:
__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc+0x15a/0x4f0 mm/slab.c:3736
kmalloc include/linux/slab.h:520 [inline]
sk_prot_alloc+0x1e2/0x2d0 net/core/sock.c:1466
sk_alloc+0x36/0x1100 net/core/sock.c:1520
l2cap_sock_alloc.constprop.0+0x31/0x210 net/bluetooth/l2cap_sock.c:1590
l2cap_sock_create+0x110/0x1b0 net/bluetooth/l2cap_sock.c:1636
bt_sock_create+0x1d0/0x470 net/bluetooth/af_bluetooth.c:130
__sock_create+0x495/0x820 net/socket.c:1276
sock_create net/socket.c:1316 [inline]
__sys_socket+0xef/0x200 net/socket.c:1346
__do_sys_socket net/socket.c:1355 [inline]
__se_sys_socket net/socket.c:1353 [inline]
__x64_sys_socket+0x6f/0xb0 net/socket.c:1353
do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 27362:
__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x250 mm/slab.c:3822
sk_prot_free net/core/sock.c:1503 [inline]
__sk_destruct+0x61d/0x830 net/core/sock.c:1584
sk_destruct net/core/sock.c:1599 [inline]
__sk_free+0x165/0x3b0 net/core/sock.c:1610
sk_free+0x3b/0x50 net/core/sock.c:1621
sock_put include/net/sock.h:1711 [inline]
l2cap_sock_kill+0xd4/0x100 net/bluetooth/l2cap_sock.c:1055
l2cap_sock_release+0xd9/0x100 net/bluetooth/l2cap_sock.c:1204
__sock_release+0xcd/0x2a0 net/socket.c:579
sock_close+0x15/0x20 net/socket.c:1140
__fput+0x2ce/0x8a0 fs/file_table.c:278
task_work_run+0x141/0x1c0 kernel/task_work.c:113
tracehook_notify_resume include/linux/tracehook.h:193 [inline]
exit_to_usermode_loop+0x269/0x2c0 arch/x86/entry/common.c:167
prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
syscall_return_slowpath arch/x86/entry/common.c:271 [inline]
do_syscall_64+0x57c/0x670 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff88808733eec0
which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 96 bytes inside of
2048-byte region [ffff88808733eec0, ffff88808733f6c0)
The buggy address belongs to the page:
page:ffffea00021ccf80 count:1 mapcount:0 mapping:ffff88812c29cc40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea00029f6a88 ffffea00023f6608 ffff88812c29cc40
raw: 0000000000000000 ffff88808733e640 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88808733ee00: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff88808733ee80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
>ffff88808733ef00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88808733ef80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808733f000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
Bluetooth: hci3: command 0x0405 tx timeout


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: d09b8017 Linux 4.19.147
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11515707900000
kernel config: https://syzkaller.appspot.com/x/.config?x=47cc70be3c316a0a

dashboard link: https://syzkaller.appspot.com/bug?extid=b673a563b3a339728b15
compiler: gcc (GCC) 10.1.0-syz 20200507

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12000bd9900000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12eacdab900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b673a5...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in constant_test_bit arch/x86/include/asm/bitops.h:317 [inline]
BUG: KASAN: use-after-free in sock_flag include/net/sock.h:839 [inline]
BUG: KASAN: use-after-free in l2cap_sock_kill+0xdb/0x100 net/bluetooth/l2cap_sock.c:1046

Read of size 8 at addr ffff88808e241660 by task kworker/0:1/6481

CPU: 0 PID: 6481 Comm: kworker/0:1 Not tainted 4.19.147-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Workqueue: events l2cap_chan_timeout

Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x22c/0x33e lib/dump_stack.c:118
print_address_description.cold+0x56/0x25c mm/kasan/report.c:256
kasan_report_error.cold+0x66/0xb9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
constant_test_bit arch/x86/include/asm/bitops.h:317 [inline]
sock_flag include/net/sock.h:839 [inline]
l2cap_sock_kill+0xdb/0x100 net/bluetooth/l2cap_sock.c:1046

l2cap_chan_timeout+0x1bb/0x210 net/bluetooth/l2cap_core.c:431
process_one_work+0x796/0x14e0 kernel/workqueue.c:2155
worker_thread+0x64c/0x1130 kernel/workqueue.c:2298
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 22133:

__do_kmalloc mm/slab.c:3727 [inline]
__kmalloc+0x15a/0x4f0 mm/slab.c:3736
kmalloc include/linux/slab.h:520 [inline]
sk_prot_alloc+0x1e2/0x2d0 net/core/sock.c:1466
sk_alloc+0x36/0x1100 net/core/sock.c:1520
l2cap_sock_alloc.constprop.0+0x31/0x210 net/bluetooth/l2cap_sock.c:1590
l2cap_sock_create+0x110/0x1b0 net/bluetooth/l2cap_sock.c:1636
bt_sock_create+0x1d0/0x470 net/bluetooth/af_bluetooth.c:130
__sock_create+0x495/0x820 net/socket.c:1276

rfcomm_l2sock_create net/bluetooth/rfcomm/core.c:203 [inline]
rfcomm_session_create net/bluetooth/rfcomm/core.c:738 [inline]
__rfcomm_dlc_open net/bluetooth/rfcomm/core.c:388 [inline]
rfcomm_dlc_open+0x6da/0xc50 net/bluetooth/rfcomm/core.c:431
rfcomm_sock_connect+0x317/0x420 net/bluetooth/rfcomm/sock.c:416
__sys_connect+0x265/0x2c0 net/socket.c:1663
__do_sys_connect net/socket.c:1674 [inline]
__se_sys_connect net/socket.c:1671 [inline]
__x64_sys_connect+0x6f/0xb0 net/socket.c:1671
do_syscall_64+0xf9/0x670 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 3608:

__cache_free mm/slab.c:3503 [inline]
kfree+0xcc/0x250 mm/slab.c:3822
sk_prot_free net/core/sock.c:1503 [inline]
__sk_destruct+0x61d/0x830 net/core/sock.c:1584
sk_destruct net/core/sock.c:1599 [inline]
__sk_free+0x165/0x3b0 net/core/sock.c:1610
sk_free+0x3b/0x50 net/core/sock.c:1621
sock_put include/net/sock.h:1711 [inline]
l2cap_sock_kill+0xd4/0x100 net/bluetooth/l2cap_sock.c:1055
l2cap_sock_release+0xd9/0x100 net/bluetooth/l2cap_sock.c:1204

__sock_release net/socket.c:579 [inline]
sock_release+0x87/0x1d0 net/socket.c:599
rfcomm_session_del+0x15a/0x1f0 net/bluetooth/rfcomm/core.c:684
rfcomm_session_close net/bluetooth/rfcomm/core.c:723 [inline]
rfcomm_process_rx net/bluetooth/rfcomm/core.c:1916 [inline]
rfcomm_process_sessions net/bluetooth/rfcomm/core.c:2000 [inline]
rfcomm_run+0x13c4/0x45d1 net/bluetooth/rfcomm/core.c:2087
kthread+0x33f/0x460 kernel/kthread.c:259
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff88808e241600

which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 96 bytes inside of

2048-byte region [ffff88808e241600, ffff88808e241e00)

The buggy address belongs to the page:

page:ffffea0002389000 count:1 mapcount:0 mapping:ffff88812c3f6c40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea00023ead88 ffffea0002387f08 ffff88812c3f6c40
raw: 0000000000000000 ffff88808e240500 0000000100000003 0000000000000000

page dumped because: kasan: bad access detected

Memory state around the buggy address:

ffff88808e241500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808e241580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808e241600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88808e241680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88808e241700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================