Subject: KASAN: use-after-free Read in hci_dev_do_open

From: syzbot <[email-masked]>
Date: Mon, 11 Jan 2021 02:24:15 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    71c061d2 Merge tag 'for-5.11-rc2-tag' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1612b248d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8aa30b9da402d224
dashboard link: https://syzkaller.appspot.com/bug?extid=8bf62d95824d213104fa
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: [email-masked]

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_read include/asm-generic/atomic-instrumented.h:27 [inline]
BUG: KASAN: use-after-free in refcount_read include/linux/refcount.h:147 [inline]
BUG: KASAN: use-after-free in skb_unref include/linux/skbuff.h:1051 [inline]
BUG: KASAN: use-after-free in kfree_skb+0x2e/0x3f0 net/core/skbuff.c:697
Read of size 4 at addr ffff888022dacc1c by task syz-executor.2/13757

CPU: 0 PID: 13757 Comm: syz-executor.2 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
 __kasan_report mm/kasan/report.c:396 [inline]
 kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
 check_memory_region_inline mm/kasan/generic.c:179 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:185
 instrument_atomic_read include/linux/instrumented.h:71 [inline]
 atomic_read include/asm-generic/atomic-instrumented.h:27 [inline]
 refcount_read include/linux/refcount.h:147 [inline]
 skb_unref include/linux/skbuff.h:1051 [inline]
 kfree_skb+0x2e/0x3f0 net/core/skbuff.c:697
 hci_dev_do_open+0xa4a/0x1a00 net/bluetooth/hci_core.c:1619
 hci_dev_open+0x132/0x300 net/bluetooth/hci_core.c:1685
 hci_sock_ioctl+0x5b6/0x840 net/bluetooth/hci_sock.c:1025
 sock_do_ioctl+0xcb/0x2d0 net/socket.c:1037
 sock_ioctl+0x477/0x6a0 net/socket.c:1177
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:739
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e087
Code: 48 83 c4 08 48 89 d8 5b 5d c3 66 0f 1f 84 00 00 00 00 00 48 89 e8 48 f7 d8 48 39 c3 0f 92 c0 eb 92 66 90 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 6d b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fffdcd39c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045e087
RDX: 0000000000000002 RSI: 00000000400448c9 RDI: 0000000000000003
RBP: 00007fffdcd39ca0 R08: 0000000000000000 R09: 00007f60a0a24700
R10: 00007f60a0a249d0 R11: 0000000000000246 R12: 000000000310e914
R13: 0000000000000004 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8498:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:46 [inline]
 set_alloc_info mm/kasan/common.c:401 [inline]
 ____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429
 kasan_slab_alloc include/linux/kasan.h:205 [inline]
 slab_post_alloc_hook mm/slab.h:512 [inline]
 slab_alloc_node mm/slub.c:2891 [inline]
 slab_alloc mm/slub.c:2899 [inline]
 kmem_cache_alloc+0x1c6/0x440 mm/slub.c:2904
 skb_clone+0x14f/0x3c0 net/core/skbuff.c:1449
 hci_cmd_work+0x18f/0x390 net/bluetooth/hci_core.c:5007
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

Freed by task 2042:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:356
 ____kasan_slab_free+0xe1/0x110 mm/kasan/common.c:362
 kasan_slab_free include/linux/kasan.h:188 [inline]
 slab_free_hook mm/slub.c:1547 [inline]
 slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1580
 slab_free mm/slub.c:3142 [inline]
 kmem_cache_free+0x82/0x350 mm/slub.c:3158
 kfree_skbmem+0xef/0x1b0 net/core/skbuff.c:627
 __kfree_skb net/core/skbuff.c:684 [inline]
 kfree_skb net/core/skbuff.c:701 [inline]
 kfree_skb+0x140/0x3f0 net/core/skbuff.c:695
 hci_cmd_work+0x182/0x390 net/bluetooth/hci_core.c:5005
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

The buggy address belongs to the object at ffff888022dacb40
 which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 220 bytes inside of
 232-byte region [ffff888022dacb40, ffff888022dacc28)
The buggy address belongs to the page:
page:00000000530f5d7f refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x22dac
flags: 0xfff00000000200(slab)
raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888010cb4c80
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888022dacb00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff888022dacb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888022dacc00: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff888022dacc80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888022dacd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
==================================================================

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