[syzbot] KASAN: use-after-free Write in h4_recv_buf

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 280d542f Merge tag 'drm-fixes-2021-03-05' of git://anongit..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f818a2d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=2d28ee81eb70698
dashboard link: https://syzkaller.appspot.com/bug?extid=1e678fbc60167d46f2a5
compiler: Debian clang version 11.0.1-2

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+1e678f...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in skb_put_data include/linux/skbuff.h:2293 [inline]
BUG: KASAN: use-after-free in h4_recv_buf+0x3d5/0xd00 drivers/bluetooth/hci_h4.c:200
Write of size 1 at addr ffff88806243d00c by task syz-executor.0/10259

CPU: 0 PID: 10259 Comm: syz-executor.0 Not tainted 5.12.0-rc1-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+0x176/0x24e lib/dump_stack.c:120
print_address_description+0x5f/0x3a0 mm/kasan/report.c:232
__kasan_report mm/kasan/report.c:399 [inline]
kasan_report+0x15e/0x210 mm/kasan/report.c:416
check_region_inline mm/kasan/generic.c:135 [inline]
kasan_check_range+0x2b5/0x2f0 mm/kasan/generic.c:186
memcpy+0x3c/0x60 mm/kasan/shadow.c:66
skb_put_data include/linux/skbuff.h:2293 [inline]
h4_recv_buf+0x3d5/0xd00 drivers/bluetooth/hci_h4.c:200
h4_recv+0xf4/0x1b0 drivers/bluetooth/hci_h4.c:115
hci_uart_tty_receive+0x157/0x490 drivers/bluetooth/hci_ldisc.c:613
tiocsti drivers/tty/tty_io.c:2317 [inline]
tty_ioctl+0xc64/0x15f0 drivers/tty/tty_io.c:2718
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x465f69
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb4a52aa188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465f69
RDX: 0000000020000000 RSI: 0000000000005412 RDI: 0000000000000003
RBP: 00000000004bfa67 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007ffc4fc6b23f R14: 00007fb4a52aa300 R15: 0000000000022000

Allocated by task 0:
(stack is not available)

Freed by task 9934:
kasan_save_stack mm/kasan/common.c:38 [inline]
kasan_set_track+0x3d/0x70 mm/kasan/common.c:46
kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:357
____kasan_slab_free+0x100/0x140 mm/kasan/common.c:360
kasan_slab_free include/linux/kasan.h:199 [inline]
slab_free_hook mm/slub.c:1562 [inline]
slab_free_freelist_hook+0x171/0x270 mm/slub.c:1600
slab_free mm/slub.c:3161 [inline]
kfree+0xcf/0x2d0 mm/slub.c:4213
skb_release_all net/core/skbuff.c:725 [inline]
__kfree_skb+0x56/0x1d0 net/core/skbuff.c:739
h4_recv_buf+0xcdb/0xd00 include/net/bluetooth/bluetooth.h:390
h4_recv+0xf4/0x1b0 drivers/bluetooth/hci_h4.c:115
hci_uart_tty_receive+0x157/0x490 drivers/bluetooth/hci_ldisc.c:613
tty_ldisc_receive_buf+0x12b/0x170 drivers/tty/tty_buffer.c:465
tty_port_default_receive_buf+0x6a/0x90 drivers/tty/tty_port.c:38
receive_buf drivers/tty/tty_buffer.c:481 [inline]
flush_to_ldisc+0x2f2/0x510 drivers/tty/tty_buffer.c:533
process_one_work+0x789/0xfd0 kernel/workqueue.c:2275
worker_thread+0xac1/0x1300 kernel/workqueue.c:2421
kthread+0x39a/0x3c0 kernel/kthread.c:292
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

The buggy address belongs to the object at ffff88806243d000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 12 bytes inside of
2048-byte region [ffff88806243d000, ffff88806243d800)
The buggy address belongs to the page:
page:000000004c9987b8 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x62438
head:000000004c9987b8 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head)
raw: 00fff00000010200 dead000000000100 dead000000000122 ffff888010842000
raw: 0000000000000000 0000000080080008 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88806243cf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88806243cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88806243d000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88806243d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88806243d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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[Hillf Danton]

Tue, 09 Mar 2021 08:07:18 -0800

Fix uaf by serializing ioctl and workqueue work pathes.
Thoughts for serialization in the tty layer are appriecated.

--- x/drivers/bluetooth/hci_h4.c
+++ y/drivers/bluetooth/hci_h4.c
@@ -112,14 +112,28 @@ static int h4_recv(struct hci_uart *hu,
if (!test_bit(HCI_UART_REGISTERED, &hu->flags))
return -EUNATCH;

+ /* serialize ioctl and workqueue pathes
+
+ ioctl work
+ ----- ----
+ tty_ioctl flush_to_ldisc
+ tiocsti receive_buf
+ hci_uart_tty_receive tty_port_default_receive_buf
+ h4_recv tty_ldisc_receive_buf
+ hci_uart_tty_receive
+ h4_recv
+ */
+ mutex_lock(&hu->buf_mutex);
+
h4->rx_skb = h4_recv_buf(hu->hdev, h4->rx_skb, data, count,
h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
if (IS_ERR(h4->rx_skb)) {
int err = PTR_ERR(h4->rx_skb);
bt_dev_err(hu->hdev, "Frame reassembly failed (%d)", err);
h4->rx_skb = NULL;
- return err;
+ count = err;
}
+ mutex_unlock(&hu->buf_mutex);

return count;
}
--- x/drivers/bluetooth/hci_uart.h
+++ y/drivers/bluetooth/hci_uart.h
@@ -67,6 +67,7 @@ struct hci_uart {
struct hci_dev *hdev;
unsigned long flags;
unsigned long hdev_flags;
+ struct mutex buf_mutex;

struct work_struct init_ready;
struct work_struct write_work;
--- x/drivers/bluetooth/hci_ldisc.c
+++ y/drivers/bluetooth/hci_ldisc.c
@@ -500,6 +500,7 @@ static int hci_uart_tty_open(struct tty_
hu->alignment = 1;
hu->padding = 0;

+ mutex_init(&hu->buf_mutex);
INIT_WORK(&hu->init_ready, hci_uart_init_work);
INIT_WORK(&hu->write_work, hci_uart_write_work);

[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.