UBUNTU-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.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
53 explicit affected versions
116 explicit affected versions
45 explicit affected versions
63 explicit affected versions
50 explicit affected versions
6 explicit affected versions
12 explicit affected versions
19 explicit affected versions
6 explicit affected versions
73 explicit affected versions
24 explicit affected versions
58 explicit affected versions
91 explicit affected versions
66 explicit affected versions
59 explicit affected versions
10 explicit affected versions
17 explicit affected versions
24 explicit affected versions
65 explicit affected versions
7 explicit affected versions
64 explicit affected versions
21 explicit affected versions
13 explicit affected versions
85 explicit affected versions
23 explicit affected versions
35 explicit affected versions
25 explicit affected versions
23 explicit affected versions
18 explicit affected versions
24 explicit affected versions
118 explicit affected versions
64 explicit affected versions
26 explicit affected versions
120 explicit affected versions
13 explicit affected versions
4 explicit affected versions
23 explicit affected versions
31 explicit affected versions
124 explicit affected versions
1 explicit affected versions
1 explicit affected versions
21 explicit affected versions
16 explicit affected versions
10 explicit affected versions
76 explicit affected versions
27 explicit affected versions
5 explicit affected versions
7 explicit affected versions
12 explicit affected versions
111 explicit affected versions
4 explicit affected versions
56 explicit affected versions
12 explicit affected versions
14 explicit affected versions
1 explicit affected versions
7 explicit affected versions
2 explicit affected versions
104 explicit affected versions
12 explicit affected versions
105 explicit affected versions
12 explicit affected versions
21 explicit affected versions
19 explicit affected versions
18 explicit affected versions
13 explicit affected versions
10 explicit affected versions
37 explicit affected versions
5 explicit affected versions
13 explicit affected versions
19 explicit affected versions
10 explicit affected versions
40 explicit affected versions
1 explicit affected versions
26 explicit affected versions
13 explicit affected versions
14 explicit affected versions
1 explicit affected versions
29 explicit affected versions
111 explicit affected versions
13 explicit affected versions
70 explicit affected versions
20 explicit affected versions
21 explicit affected versions
1 explicit affected versions
100 explicit affected versions
65 explicit affected versions
28 explicit affected versions
33 explicit affected versions
23 explicit affected versions
10 explicit affected versions
1 explicit affected versions
11 explicit affected versions
12 explicit affected versions
7 explicit affected versions
12 explicit affected versions
138 explicit affected versions
56 explicit affected versions
50 explicit affected versions
132 explicit affected versions
66 explicit affected versions
154 explicit affected versions
10 explicit affected versions
26 explicit affected versions
25 explicit affected versions
1 explicit affected versions
14 explicit affected versions
26 explicit affected versions
13 explicit affected versions
26 explicit affected versions
139 explicit affected versions
78 explicit affected versions
16 explicit affected versions
67 explicit affected versions
29 explicit affected versions
54 explicit affected versions
116 explicit affected versions
3 explicit affected versions
132 explicit affected versions
93 explicit affected versions
1 explicit affected versions
4 explicit affected versions
2 explicit affected versions
51 explicit affected versions
92 explicit affected versions
13 explicit affected versions
23 explicit affected versions
12 explicit affected versions
53 explicit affected versions
27 explicit affected versions
40 explicit affected versions
121 explicit affected versions
1 explicit affected versions
1 explicit affected versions
98 explicit affected versions
22 explicit affected versions
8 explicit affected versions
30 explicit affected versions
5 explicit affected versions
8 explicit affected versions
1 explicit affected versions
10 explicit affected versions
4 explicit affected versions
25 explicit affected versions
13 explicit affected versions
110 explicit affected versions
13 explicit affected versions
72 explicit affected versions
7 explicit affected versions
140 explicit affected versions
3 explicit affected versions
94 explicit affected versions
57 explicit affected versions
10 explicit affected versions
12 explicit affected versions
15 explicit affected versions
108 explicit affected versions
80 explicit affected versions
56 explicit affected versions
44 explicit affected versions
16 explicit affected versions
3 explicit affected versions
13 explicit affected versions
26 explicit affected versions
45 explicit affected versions
37 explicit affected versions
30 explicit affected versions
14 explicit affected versions
38 explicit affected versions
167 explicit affected versions
9 explicit affected versions
55 explicit affected versions
11 explicit affected versions
19 explicit affected versions
7 explicit affected versions
66 explicit affected versions
7 explicit affected versions
35 explicit affected versions
121 explicit affected versions
4 explicit affected versions
1 explicit affected versions
1 explicit affected versions
1 explicit affected versions
64 explicit affected versions
56 explicit affected versions
13 explicit affected versions
43 explicit affected versions
77 explicit affected versions
119 explicit affected versions
10 explicit affected versions
8 explicit affected versions
24 explicit affected versions
88 explicit affected versions
14 explicit affected versions
4 explicit affected versions
78 explicit affected versions
11 explicit affected versions
1 explicit affected versions
69 explicit affected versions
123 explicit affected versions
19 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/b06f388994500297bb91be60ffaf6825ecfd2afe
- 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://ubuntu.com/security/CVE-2025-21820
- https://ubuntu.com/security/notices/USN-7510-1
- https://ubuntu.com/security/notices/USN-7510-2
- https://ubuntu.com/security/notices/USN-7510-3
- https://ubuntu.com/security/notices/USN-7510-4
- https://ubuntu.com/security/notices/USN-7510-5
- https://ubuntu.com/security/notices/USN-7510-6
- https://ubuntu.com/security/notices/USN-7510-7
- https://ubuntu.com/security/notices/USN-7510-8
- https://ubuntu.com/security/notices/USN-7511-1
- https://ubuntu.com/security/notices/USN-7511-2
- https://ubuntu.com/security/notices/USN-7511-3
- https://ubuntu.com/security/notices/USN-7512-1
- https://ubuntu.com/security/notices/USN-7521-1
- https://ubuntu.com/security/notices/USN-7521-2
- https://ubuntu.com/security/notices/USN-7521-3
- https://ubuntu.com/security/notices/USN-7593-1
- https://ubuntu.com/security/notices/USN-7602-1
- https://ubuntu.com/security/notices/USN-7651-1
- https://ubuntu.com/security/notices/USN-7651-2
- https://ubuntu.com/security/notices/USN-7651-3
- https://ubuntu.com/security/notices/USN-7651-4
- https://ubuntu.com/security/notices/USN-7651-5
- https://ubuntu.com/security/notices/USN-7651-6
- https://ubuntu.com/security/notices/USN-7652-1
- https://ubuntu.com/security/notices/USN-7653-1
- https://ubuntu.com/security/notices/USN-7737-1
- https://www.cve.org/CVERecord?id=CVE-2025-21820