In the Linux kernel, the following vulnerability has been resolved: fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling A SOFTIRQ-safe to SOFTIRQ-unsafe lock order deadlock can occur in send_sigio() and send_sigurg() when a process group receives a signal. When FASYNC is configured for a process group (PIDTYPE_PGID), both functions use read_lock(&tasklist_lock) to traverse the task list. However, they are frequently called from softirq context: - send_sigio() via input_inject_event -> kill_fasync - send_sigurg() via tcp_check_urg -> sk_send_sigurg (NET_RX_SOFTIRQ) The deadlock is caused by the rwlock writer fairness mechanism: 1. CPU 0 (process context) holds read_lock(&tasklist_lock) in do_wait(). 2. CPU 1 (process context) attempts write_lock(&tasklist_lock) in fork() or exit() and spins, which blocks all new readers. 3. CPU 0 is interrupted by a softirq (e.g., TCP URG packet reception). 4. The softirq calls send_sigurg() and attempts to acquire read_lock(&tasklist_lock), deadlocking because CPU 1 is waiting. Since PID hashing and do_each_pid_task() traversals are already RCU-protected, the read_lock on tasklist_lock is no longer strictly required for safe traversal. Fix this by replacing tasklist_lock with rcu_read_lock(), aligning the process group signaling path with the single-PID path. This also mitigates a potential remote denial of service vector via TCP URG packets. Lockdep splat: ===================================================== WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected [...] Chain exists of: &dev->event_lock --> &f_owner->lock --> tasklist_lock Possible interrupt unsafe locking scenario: CPU0 CPU1 ---- ---- lock(tasklist_lock); local_irq_disable(); lock(&dev->event_lock); lock(&f_owner->lock); <Interrupt> lock(&dev->event_lock); *** DEADLOCK ***
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
| Attack Vector | NETWORK |
|---|---|
| Attack Complexity | LOW |
| Privileges Required | NONE |
| User Interaction | NONE |
| Scope | UNCHANGED |
| Confidentiality Impact | NONE |
| Integrity Impact | NONE |
| Availability Impact | HIGH |
Source: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Type: Secondary
Exploitability Score: 3.9
Impact Score: 3.6
| Source | Type | Description |
|---|---|---|
| [email protected] | Primary |
en
CWE-667
|
| Vendor | Product | Version | Update | Type |
|---|---|---|---|---|
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59cbac0> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59c8040> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d239fbe82c0> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59c94c0> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59c9500> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d239fbeb900> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59cbc80> | Operating System |
| linux | linux_kernel | * | <built-in method update of dict object at 0x7d23a59cac40> | Operating System |
| linux | linux_kernel | 2.6.12 | <built-in method update of dict object at 0x7d23a59cba00> | Operating System |
| linux | linux_kernel | 2.6.12 | <built-in method update of dict object at 0x7d23a59c9d00> | Operating System |
| linux | linux_kernel | 2.6.12 | <built-in method update of dict object at 0x7d239fbeb400> | Operating System |
| linux | linux_kernel | 2.6.12 | <built-in method update of dict object at 0x7d23a59c8880> | Operating System |
| linux | linux_kernel | 2.6.12 | <built-in method update of dict object at 0x7d239fbe8d40> | Operating System |
| Vulnerable | CPE |
|---|---|
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:2.6.12:-:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:2.6.12:rc2:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:2.6.12:rc3:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:2.6.12:rc4:*:*:*:*:*:* |
| Yes | cpe:2.3:o:linux:linux_kernel:2.6.12:rc5:*:*:*:*:*:* |