print_worker_info() includes no validity check on the pwq and wq pointers before handing them over to the probe_kernel_read() functions. It seems that most architectures don't care about that, but at least on the parisc architecture this leads to a kernel crash since accesses to page zero are protected by the kernel for security reasons. Fix this problem by verifying the contents of pwq and wq before usage. Even if probe_kernel_read() usually prevents such crashes by disabling page faults, clean code should always include such checks. Without this fix issuing "echo t > /proc/sysrq-trigger" will immediately crash the Linux kernel on the parisc architecture. CC: Tejun Heo <tj@xxxxxxxxxx> CC: Libin <huawei.libin@xxxxxxxxxx> CC: linux-parisc@xxxxxxxxxxxxxxx CC: James.Bottomley@xxxxxxxxxxxxxxxxxxxxx Signed-off-by: Helge Deller <deller@xxxxxx> diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 987293d..c03b47f 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4512,8 +4512,10 @@ void print_worker_info(const char *log_lvl, struct task_struct *task) */ probe_kernel_read(&fn, &worker->current_func, sizeof(fn)); probe_kernel_read(&pwq, &worker->current_pwq, sizeof(pwq)); - probe_kernel_read(&wq, &pwq->wq, sizeof(wq)); - probe_kernel_read(name, wq->name, sizeof(name) - 1); + if (pwq) + probe_kernel_read(&wq, &pwq->wq, sizeof(wq)); + if (wq) + probe_kernel_read(name, wq->name, sizeof(name) - 1); /* copy worker description */ probe_kernel_read(&desc_valid, &worker->desc_valid, sizeof(desc_valid)); -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
