From 59b33f148cc08fb33cbe823fca1e34f7f023765e Mon Sep 17 00:00:00 2001 From: Helge Deller Date: Tue, 1 Oct 2013 21:54:46 +0200 Subject: [PATCH] parisc: fix interruption handler to respect pagefault_disable() Running an "echo t > /proc/sysrq-trigger" crashes the parisc kernel. The problem is, that in print_worker_info() we try to read the workqueue info via the probe_kernel_read() functions which use pagefault_disable() to avoid crashes like this: 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); The problem here is, that the first probe_kernel_read(&pwq) might return zero in pwq and as such the following probe_kernel_reads() try to access contents of the page zero which is read protected and generate a kernel segfault. With this patch we fix the interruption handler to call parisc_terminate() directly only if pagefault_disable() was not called (in which case preempt_count()==0). Otherwise we hand over to the pagefault handler which will try to look up the faulting address in the fixup tables. Signed-off-by: Helge Deller Cc: # v3.0+ Signed-off-by: John David Anglin Signed-off-by: Helge Deller --- arch/parisc/kernel/traps.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/parisc/kernel/traps.c b/arch/parisc/kernel/traps.c index ebc877c28583..1cd1d0c83b6d 100644 --- a/arch/parisc/kernel/traps.c +++ b/arch/parisc/kernel/traps.c @@ -800,14 +800,14 @@ void notrace handle_interruption(int code, struct pt_regs *regs) else { /* - * The kernel should never fault on its own address space. + * The kernel should never fault on its own address space, + * unless pagefault_disable() was called before. */ - if (fault_space == 0) + if (fault_space == 0 && !in_atomic()) { pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC); parisc_terminate("Kernel Fault", regs, code, fault_address); - } } -- 2.30.2