CVE-2025-21820

tty: xilinx_uartps: split sysrq handling

Description

In the Linux kernel, the following vulnerability has been resolved: tty: xilinx_uartps: split sysrq handling lockdep detects the following circular locking dependency: CPU 0 CPU 1 ========================== ============================ cdns_uart_isr() printk() uart_port_lock(port) console_lock() cdns_uart_console_write() if (!port->sysrq) uart_port_lock(port) uart_handle_break() port->sysrq = ... uart_handle_sysrq_char() printk() console_lock() The fixed commit attempts to avoid this situation by only taking the port lock in cdns_uart_console_write if port->sysrq unset. However, if (as shown above) cdns_uart_console_write runs before port->sysrq is set, then it will try to take the port lock anyway. This may result in a deadlock. Fix this by splitting sysrq handling into two parts. We use the prepare helper under the port lock and defer handling until we release the lock.

Category

5.5
CVSS
Severity: Medium
CVSS 3.1 •
EPSS 0.02%
Affected: Linux Linux
Affected: Linux Linux
Published at:
Updated at:

References

Link Tags
https://git.kernel.org/stable/c/e22a97700901ba5e8bf8db68056a0d50f9440cae
https://git.kernel.org/stable/c/de5bd24197bd9ee37ec1e379a3d882bbd15c5065 patch
https://git.kernel.org/stable/c/8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c patch
https://git.kernel.org/stable/c/9b88a7c4584ba67267a051069b8abe44fc9595b2 patch
https://git.kernel.org/stable/c/4410dba9807a17a93f649a9f5870ceaf30a675a3 patch
https://git.kernel.org/stable/c/b06f388994500297bb91be60ffaf6825ecfd2afe patch

Frequently Asked Questions

What is the severity of CVE-2025-21820?
CVE-2025-21820 has been scored as a medium severity vulnerability.
How to fix CVE-2025-21820?
To fix CVE-2025-21820, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2025-21820 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2025-21820 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2025-21820?
CVE-2025-21820 affects Linux Linux, Linux Linux.
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