Subject: KASAN: use-after-free Write in sco_chan_del

From: syzbot <[email-masked]>
Date: Sun, 02 Aug 2020 22:05:26 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    ac3a0c84 Merge git://git.kernel.org/pub/scm/linux/kernel/g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11638a42900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c0cfcf935bcc94d2
dashboard link: https://syzkaller.appspot.com/bug?extid=8f6017ee5c7fb9515782
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17fd776c900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15ac7014900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:748 [inline]
BUG: KASAN: use-after-free in hci_conn_drop include/net/bluetooth/hci_core.h:1049 [inline]
BUG: KASAN: use-after-free in sco_chan_del+0xe6/0x430 net/bluetooth/sco.c:148
Write of size 4 at addr ffff8880a03d8010 by task syz-executor104/6978

CPU: 1 PID: 6978 Comm: syz-executor104 Not tainted 5.8.0-rc7-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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 atomic_dec_and_test include/asm-generic/atomic-instrumented.h:748 [inline]
 hci_conn_drop include/net/bluetooth/hci_core.h:1049 [inline]
 sco_chan_del+0xe6/0x430 net/bluetooth/sco.c:148
 __sco_sock_close+0x16e/0x5b0 net/bluetooth/sco.c:433
 sco_sock_close net/bluetooth/sco.c:447 [inline]
 sco_sock_release+0x69/0x290 net/bluetooth/sco.c:1021
 __sock_release+0xcd/0x280 net/socket.c:605
 sock_close+0x18/0x20 net/socket.c:1278
 __fput+0x33c/0x880 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb72/0x2a40 kernel/exit.c:805
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x40b/0x1ee0 kernel/signal.c:2743
 do_signal+0x82/0x2520 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:235 [inline]
 __prepare_exit_to_usermode+0x156/0x1f0 arch/x86/entry/common.c:269
 do_syscall_64+0x6c/0xe0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x446e69
Code: Bad RIP value.
RSP: 002b:00007fff15a45008 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: fffffffffffffffc RBX: 0000000000000000 RCX: 0000000000446e69
RDX: 0000000000000008 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 0000000000000004 R08: 0000000000000002 R09: 00000003000100ff
R10: 0000000000000004 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000407ac0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6978:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
 kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 hci_conn_add+0x53/0x1340 net/bluetooth/hci_conn.c:525
 hci_connect_sco+0x350/0x860 net/bluetooth/hci_conn.c:1279
 sco_connect net/bluetooth/sco.c:240 [inline]
 sco_sock_connect+0x308/0x980 net/bluetooth/sco.c:576
 __sys_connect_file+0x155/0x1a0 net/socket.c:1854
 __sys_connect+0x160/0x190 net/socket.c:1871
 __do_sys_connect net/socket.c:1882 [inline]
 __se_sys_connect net/socket.c:1879 [inline]
 __x64_sys_connect+0x6f/0xb0 net/socket.c:1879
 do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6972:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3757
 device_release+0x71/0x200 drivers/base/core.c:1579
 kobject_cleanup lib/kobject.c:693 [inline]
 kobject_release lib/kobject.c:722 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1c0/0x270 lib/kobject.c:739
 put_device+0x1b/0x30 drivers/base/core.c:2799
 hci_conn_del+0x27e/0x6a0 net/bluetooth/hci_conn.c:645
 hci_phy_link_complete_evt.isra.0+0x508/0x790 net/bluetooth/hci_event.c:4921
 hci_event_packet+0x481a/0x86f5 net/bluetooth/hci_event.c:6180
 hci_rx_work+0x22e/0xb10 net/bluetooth/hci_core.c:4705
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff8880a03d8000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 16 bytes inside of
 4096-byte region [ffff8880a03d8000, ffff8880a03d9000)
The buggy address belongs to the page:
page:ffffea000280f600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea000280f600 order:1 compound_mapcount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea0002882888 ffffea00027ede08 ffff8880aa002000
raw: 0000000000000000 ffff8880a03d8000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a03d7f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
 ffff8880a03d7f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a03d8000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff8880a03d8080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a03d8100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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