Release Date: | 2025-07-09 | |
Impact: | Moderate | What is this? |
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_core: Fix use-after-free in vhci_flush()
syzbot reported use-after-free in vhci_flush() without repro. [0]
From the splat, a thread close()d a vhci file descriptor while
its device was being used by iotcl() on another thread.
Once the last fd refcnt is released, vhci_release() calls
hci_unregister_dev(), hci_free_dev(), and kfree() for struct
vhci_data, which is set to hci_dev->dev->driver_data.
The problem is that there is no synchronisation after unlinking
hdev from hci_dev_list in hci_unregister_dev(). There might be
another thread still accessing the hdev which was fetched before
the unlink operation.
We can use SRCU for such synchronisation.
Let's run hci_dev_reset() under SRCU and wait for its completion
in hci_unregister_dev().
Another option would be to restore hci_dev->destruct(), which was
removed in commit 587ae086f6e4 ("Bluetooth: Remove unused
hci-destruct cb"). However, this would not be a good solution, as
we should not run hci_unregister_dev() while there are in-flight
ioctl() requests, which could lead to another data-race KCSAN splat.
Note that other drivers seem to have the same problem, for exmaple,
virtbt_remove().
[0]:
BUG: KASAN: slab-use-after-free in skb_queue_empty_lockless include/linux/skbuff.h:1891 [inline]
BUG: KASAN: slab-use-after-free in skb_queue_purge_reason+0x99/0x360 net/core/skbuff.c:3937
Read of size 8 at addr ffff88807cb8d858 by task syz.1.219/6718
CPU: 1 UID: 0 PID: 6718 Comm: syz.1.219 Not tainted 6.16.0-rc1-syzkaller-00196-g08207f42d3ff #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
See more information about CVE-2025-38250 from MITRE CVE dictionary and NIST NVD
NOTE: The following CVSS metrics and score provided are preliminary and subject to review.
Base Score: | 7.3 |
Vector String: | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H |
Version: | 3.1 |
Attack Vector: | Local |
Attack Complexity: | Low |
Privileges Required: | Low |
User Interaction: | None |
Scope: | Unchanged |
Confidentiality Impact: | High |
Integrity Impact: | Low |
Availability Impact: | High |
Platform | Errata | Release Date |
Oracle Linux version 10 (kernel) | ELSA-2025-14009 | 2025-08-21 |
Oracle Linux version 10 (kernel-uek) | ELSA-2025-20551 | 2025-09-08 |
Oracle Linux version 8 (kernel) | ELSA-2025-13960 | 2025-08-18 |
Oracle Linux version 9 (kernel) | ELSA-2025-13962 | 2025-08-19 |
Oracle Linux version 9 (kernel-uek) | ELSA-2025-20551 | 2025-09-08 |
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