CVE-2025-38262

In the Linux kernel, the following vulnerability has been resolved:

tty: serial: uartlite: register uart driver in init

When two instances of uart devices are probing, a concurrency race can occur. If one thread calls uart_register_driver function, which first allocates and assigns memory to 'uart_state' member of uart_driver structure, the other instance can bypass uart driver registration and call ulite_assign. This calls uart_add_one_port, which expects the uart driver to be fully initialized. This leads to a kernel panic due to a null pointer dereference:

[ 8.143581] BUG: kernel NULL pointer dereference, address: 00000000000002b8 [ 8.156982] #PF: supervisor write access in kernel mode [ 8.156984] #PF: error_code(0x0002) - not-present page [ 8.156986] PGD 0 P4D 0 ... [ 8.180668] RIP: 0010:mutex_lock+0x19/0x30 [ 8.188624] Call Trace: [ 8.188629] ? __die_body.cold+0x1a/0x1f [ 8.195260] ? page_fault_oops+0x15c/0x290 [ 8.209183] ? __irq_resolve_mapping+0x47/0x80 [ 8.209187] ? exc_page_fault+0x64/0x140 [ 8.209190] ? asm_exc_page_fault+0x22/0x30 [ 8.209196] ? mutex_lock+0x19/0x30 [ 8.223116] uart_add_one_port+0x60/0x440 [ 8.223122] ? proc_tty_register_driver+0x43/0x50 [ 8.223126] ? tty_register_driver+0x1ca/0x1e0 [ 8.246250] ulite_probe+0x357/0x4b0 [uartlite]

To prevent it, move uart driver registration in to init function. This will ensure that uart_driver is always registered when probe function is called.

A low severity concurrency flaw was found in the Linux kernel's uartlite serial driver. When two instances of uartlite UART devices are probed concurrently, one thread may call uart_register_driver while another instance bypasses driver registration and calls uart_add_one_port before the uart_driver structure is fully initialized. This results in a NULL pointer dereference that causes a kernel panic, so the issue affects system availability only; confidentiality and integrity are not impacted. Exploitation requires privileged local access on a system where multiple uartlite UART devices are being probed, which limits practical exposure.

Red Hat Product Security rated this issue as Low severity (CVSS 4.1, AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H), lower than the NIST (5.5) and CVE.org (7.8) scores, because triggering the race requires privileged local access, a narrow timing window, and hardware that exposes multiple uartlite instances.

The kernel and kernel-rt packages in Red Hat Enterprise Linux 8, 9, and 10 are affected. The fix is currently deferred because of the low impact and limited practical exploitability; the residual risk is a local denial of service (kernel panic) on systems using the uartlite driver during concurrent device probing. Red Hat Enterprise Linux 6 and 7 Extended Lifecycle Support and Red Hat In-Vehicle OS are not affected because the vulnerable code is not present in those products.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.