Vulnerability Details : CVE-2021-47038
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: avoid deadlock between hci_dev->lock and socket lock
Commit eab2404ba798 ("Bluetooth: Add BT_PHY socket option") added a
dependency between socket lock and hci_dev->lock that could lead to
deadlock.
It turns out that hci_conn_get_phy() is not in any way relying on hdev
being immutable during the runtime of this function, neither does it even
look at any of the members of hdev, and as such there is no need to hold
that lock.
This fixes the lockdep splat below:
======================================================
WARNING: possible circular locking dependency detected
5.12.0-rc1-00026-g73d464503354 #10 Not tainted
------------------------------------------------------
bluetoothd/1118 is trying to acquire lock:
ffff8f078383c078 (&hdev->lock){+.+.}-{3:3}, at: hci_conn_get_phy+0x1c/0x150 [bluetooth]
but task is already holding lock:
ffff8f07e831d920 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: l2cap_sock_getsockopt+0x8b/0x610
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}:
lock_sock_nested+0x72/0xa0
l2cap_sock_ready_cb+0x18/0x70 [bluetooth]
l2cap_config_rsp+0x27a/0x520 [bluetooth]
l2cap_sig_channel+0x658/0x1330 [bluetooth]
l2cap_recv_frame+0x1ba/0x310 [bluetooth]
hci_rx_work+0x1cc/0x640 [bluetooth]
process_one_work+0x244/0x5f0
worker_thread+0x3c/0x380
kthread+0x13e/0x160
ret_from_fork+0x22/0x30
-> #2 (&chan->lock#2/1){+.+.}-{3:3}:
__mutex_lock+0xa3/0xa10
l2cap_chan_connect+0x33a/0x940 [bluetooth]
l2cap_sock_connect+0x141/0x2a0 [bluetooth]
__sys_connect+0x9b/0xc0
__x64_sys_connect+0x16/0x20
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #1 (&conn->chan_lock){+.+.}-{3:3}:
__mutex_lock+0xa3/0xa10
l2cap_chan_connect+0x322/0x940 [bluetooth]
l2cap_sock_connect+0x141/0x2a0 [bluetooth]
__sys_connect+0x9b/0xc0
__x64_sys_connect+0x16/0x20
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
-> #0 (&hdev->lock){+.+.}-{3:3}:
__lock_acquire+0x147a/0x1a50
lock_acquire+0x277/0x3d0
__mutex_lock+0xa3/0xa10
hci_conn_get_phy+0x1c/0x150 [bluetooth]
l2cap_sock_getsockopt+0x5a9/0x610 [bluetooth]
__sys_getsockopt+0xcc/0x200
__x64_sys_getsockopt+0x20/0x30
do_syscall_64+0x33/0x80
entry_SYSCALL_64_after_hwframe+0x44/0xae
other info that might help us debug this:
Chain exists of:
&hdev->lock --> &chan->lock#2/1 --> sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
lock(&chan->lock#2/1);
lock(sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP);
lock(&hdev->lock);
*** DEADLOCK ***
1 lock held by bluetoothd/1118:
#0: ffff8f07e831d920 (sk_lock-AF_BLUETOOTH-BTPROTO_L2CAP){+.+.}-{0:0}, at: l2cap_sock_getsockopt+0x8b/0x610 [bluetooth]
stack backtrace:
CPU: 3 PID: 1118 Comm: bluetoothd Not tainted 5.12.0-rc1-00026-g73d464503354 #10
Hardware name: LENOVO 20K5S22R00/20K5S22R00, BIOS R0IET38W (1.16 ) 05/31/2017
Call Trace:
dump_stack+0x7f/0xa1
check_noncircular+0x105/0x120
? __lock_acquire+0x147a/0x1a50
__lock_acquire+0x147a/0x1a50
lock_acquire+0x277/0x3d0
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
? __lock_acquire+0x2e1/0x1a50
? lock_is_held_type+0xb4/0x120
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
__mutex_lock+0xa3/0xa10
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
? lock_acquire+0x277/0x3d0
? mark_held_locks+0x49/0x70
? mark_held_locks+0x49/0x70
? hci_conn_get_phy+0x1c/0x150 [bluetooth]
hci_conn_get_phy+0x
---truncated---
Products affected by CVE-2021-47038
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Exploit prediction scoring system (EPSS) score for CVE-2021-47038
0.04%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 5 %
Percentile, the proportion of vulnerabilities that are scored at or less
CVSS scores for CVE-2021-47038
Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source | First Seen |
---|---|---|---|---|---|---|
5.5
|
MEDIUM | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
1.8
|
3.6
|
NIST | 2024-12-06 |
CWE ids for CVE-2021-47038
-
The product does not properly acquire or release a lock on a resource, leading to unexpected resource state changes and behaviors.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-47038
-
https://git.kernel.org/stable/c/17486960d79b900c45e0bb8fbcac0262848582ba
Bluetooth: avoid deadlock between hci_dev->lock and socket lock - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/7cc0ba67883c6c8d3bddb283f56c167fc837a555
Bluetooth: avoid deadlock between hci_dev->lock and socket lock - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/332e69eb3bd90370f2d9f2c2ca7974ff523dea17
Bluetooth: avoid deadlock between hci_dev->lock and socket lock - kernel/git/stable/linux.git - Linux kernel stable treePatch
-
https://git.kernel.org/stable/c/fee71f480bc1dec5f6ae3b0b185ff12a62bceabc
Bluetooth: avoid deadlock between hci_dev->lock and socket lock - kernel/git/stable/linux.git - Linux kernel stable treePatch
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