CVE-2025-21820

tty: xilinx_uartps: split sysrq handling

MEDIUM

5.5

CVSS Score

Published: February 27, 2025 at 08:04 PM UTC

Updated: June 17, 2026 at 08:44 AM UTC

1 product affected across 1 vendorLinux Kernel

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Severity

MEDIUM5.5

Exploit prediction

EPSS 0.2%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Linux Kernel · Linux

95%

4.6 ≤ v < 5.15.1794.6 ≤ v < 6.1.1294.6 ≤ v < 6.12.144.6 ≤ v < 6.13.34.6 ≤ v < 6.144.6 ≤ v < 6.6.786.13 ≤ v < 6.13.36.2 ≤ v < 6.6.786.7 ≤ v < 6.12.144.674ea66d4ca061a3cd4c0e924e51b60e924644852

Vendor states this is fixed in 4410dba9807a17a93f649a9f5870ceaf30a675a3 (fixed)

Vendor states this is fixed in 8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c (fixed)

Vendor states this is fixed in 9b88a7c4584ba67267a051069b8abe44fc9595b2 (fixed)

Vendor states this is fixed in b06f388994500297bb91be60ffaf6825ecfd2afe (fixed)

Vendor states this is fixed in de5bd24197bd9ee37ec1e379a3d882bbd15c5065 (fixed)

Vendor states this is fixed in e22a97700901ba5e8bf8db68056a0d50f9440cae (fixed)

Vendor states this is fixed in 4.6 (unaffected)

Vendor states this is fixed in 5.15.179 (unaffected)

Vendor states this is fixed in 6.1.129 (unaffected)

Vendor states this is fixed in 6.12.14 (unaffected)

Vendor states this is fixed in 6.13.3 (unaffected)

Vendor states this is fixed in 6.14 (unaffected)