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SubjectKASAN: use-after-free Read in rfcomm_dlc_exists
From
Hello,

syzbot found the following crash on:

HEAD commit: 89cf55353308 Add linux-next specific files for 20180720
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1721408c400000
kernel config: https://syzkaller.appspot.com/x/.config?x=a9641a83a066bb43
dashboard link: https://syzkaller.appspot.com/bug?extid=728bead095cef3335bb6
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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+728bead095cef3335bb6@syzkaller.appspotmail.com

EXT4-fs (loop7): VFS: Can't find ext4 filesystem
FAT-fs (loop4): Directory bread(block 2) failed
FAT-fs (loop4): Directory bread(block 3) failed
==================================================================
BUG: KASAN: use-after-free in rfcomm_dlc_get
net/bluetooth/rfcomm/core.c:360 [inline]
BUG: KASAN: use-after-free in rfcomm_dlc_exists+0x1be/0x1f0
net/bluetooth/rfcomm/core.c:549
Read of size 1 at addr ffff8801d2c1b484 by task syz-executor7/26132

FAT-fs (loop4): Directory bread(block 4) failed
CPU: 0 PID: 26132 Comm: syz-executor7 Not tainted 4.18.0-rc5-next-20180720+
#12
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+0x1c9/0x2b4 lib/dump_stack.c:113
FAT-fs (loop4): Directory bread(block 5) failed
print_address_description+0x6c/0x20b mm/kasan/report.c:256
FAT-fs (loop4): Directory bread(block 6) failed
kasan_report_error mm/kasan/report.c:354 [inline]
kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
__asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430
rfcomm_dlc_get net/bluetooth/rfcomm/core.c:360 [inline]
rfcomm_dlc_exists+0x1be/0x1f0 net/bluetooth/rfcomm/core.c:549
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:413 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0x105e/0x2240 net/bluetooth/rfcomm/tty.c:588
FAT-fs (loop4): Directory bread(block 7) failed
FAT-fs (loop4): Directory bread(block 8) failed
rfcomm_sock_ioctl+0x89/0xb0 net/bluetooth/rfcomm/sock.c:902
sock_do_ioctl+0xe4/0x3e0 net/socket.c:951
FAT-fs (loop4): Directory bread(block 9) failed
FAT-fs (loop4): Directory bread(block 10) failed
sock_ioctl+0x30d/0x680 net/socket.c:1075
FAT-fs (loop4): Directory bread(block 11) failed
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
attempt to access beyond end of device
loop4: rw=1, want=73, limit=2
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455ab9
Code: 1d ba 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f46b0b73c68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f46b0b746d4 RCX: 0000000000455ab9
RDX: 0000000020000140 RSI: 00000000400452c8 RDI: 0000000000000014
RBP: 000000000072bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004bdaad R14: 00000000004cc4c0 R15: 0000000000000000

Allocated by task 23864:
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:707 [inline]
rfcomm_dlc_alloc+0xb8/0x490 net/bluetooth/rfcomm/core.c:305
rfcomm_sock_alloc.constprop.6+0x13a/0x420 net/bluetooth/rfcomm/sock.c:286
rfcomm_sock_create+0xf0/0x2b0 net/bluetooth/rfcomm/sock.c:329
bt_sock_create+0x16b/0x2d0 net/bluetooth/af_bluetooth.c:130
__sock_create+0x53c/0x940 net/socket.c:1268
sock_create net/socket.c:1308 [inline]
__sys_socket+0x106/0x260 net/socket.c:1338
__do_sys_socket net/socket.c:1347 [inline]
__se_sys_socket net/socket.c:1345 [inline]
__x64_sys_socket+0x73/0xb0 net/socket.c:1345
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 26096:
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
rfcomm_dlc_free+0x1e/0x30 net/bluetooth/rfcomm/core.c:328
rfcomm_dlc_put include/net/bluetooth/rfcomm.h:258 [inline]
__rfcomm_create_dev net/bluetooth/rfcomm/tty.c:417 [inline]
rfcomm_create_dev net/bluetooth/rfcomm/tty.c:486 [inline]
rfcomm_dev_ioctl+0x1dfe/0x2240 net/bluetooth/rfcomm/tty.c:588
rfcomm_sock_ioctl+0x89/0xb0 net/bluetooth/rfcomm/sock.c:902
sock_do_ioctl+0xe4/0x3e0 net/socket.c:951
sock_ioctl+0x30d/0x680 net/socket.c:1075
vfs_ioctl fs/ioctl.c:46 [inline]
file_ioctl fs/ioctl.c:501 [inline]
do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
__do_sys_ioctl fs/ioctl.c:709 [inline]
__se_sys_ioctl fs/ioctl.c:707 [inline]
__x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d2c1b340
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 324 bytes inside of
512-byte region [ffff8801d2c1b340, ffff8801d2c1b540)
The buggy address belongs to the page:
page:ffffea00074b06c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0x0
flags: 0x2fffc0000000200(slab)
raw: 02fffc0000000200 ffffea00073f55c8 ffffea0007245f88 ffff8801da800940
raw: 0000000000000000 ffff8801d2c1b0c0 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801d2c1b380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801d2c1b400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8801d2c1b480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8801d2c1b500: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8801d2c1b580: fc fc fc fc fc fc fc fc 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.
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