CVE-2025-21820

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.

The following products are affected by CVE-2025-21820 vulnerability.

Here, you will find a curated list of external links that provide in-depth information to CVE-2025-21820.

URL	Resource
https://git.kernel.org/stable/c/4410dba9807a17a93f649a9f5870ceaf30a675a3
https://git.kernel.org/stable/c/8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c
https://git.kernel.org/stable/c/9b88a7c4584ba67267a051069b8abe44fc9595b2
https://git.kernel.org/stable/c/b06f388994500297bb91be60ffaf6825ecfd2afe
https://git.kernel.org/stable/c/de5bd24197bd9ee37ec1e379a3d882bbd15c5065
https://git.kernel.org/stable/c/e22a97700901ba5e8bf8db68056a0d50f9440cae
https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
https://lore.kernel.org/linux-cve-announce/2025022710-CVE-2025-21820-f4ab@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2025-21820
https://www.cve.org/CVERecord?id=CVE-2025-21820