Commit 59b33f148cc08fb33cbe823fca1e34f7f023765e
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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 <deller@gmx.de> Cc: <stable@vger.kernel.org> # v3.0+ Signed-off-by: John David Anglin <dave.anglin@bell.net> Signed-off-by: Helge Deller <deller@gmx.de>
Showing 1 changed file with 3 additions and 3 deletions Side-by-side Diff
arch/parisc/kernel/traps.c
... | ... | @@ -800,14 +800,14 @@ |
800 | 800 | else { |
801 | 801 | |
802 | 802 | /* |
803 | - * The kernel should never fault on its own address space. | |
803 | + * The kernel should never fault on its own address space, | |
804 | + * unless pagefault_disable() was called before. | |
804 | 805 | */ |
805 | 806 | |
806 | - if (fault_space == 0) | |
807 | + if (fault_space == 0 && !in_atomic()) | |
807 | 808 | { |
808 | 809 | pdc_chassis_send_status(PDC_CHASSIS_DIRECT_PANIC); |
809 | 810 | parisc_terminate("Kernel Fault", regs, code, fault_address); |
810 | - | |
811 | 811 | } |
812 | 812 | } |
813 | 813 |