From: Eugeniy Paltsev Eugeniy.Paltsev@synopsys.com

As of today if userspace process tries to access a kernel virtual addres (0x7000_0000 to 0x7ffff_ffff) such that a legit kernel mapping already exists, that process hangs instead of being killed with SIGSEGV

Fix that by ensuring that do_page_fault() handles kenrel vaddr only if in kernel mode.

And given this, we can also simplify the code a bit. Now a vmalloc fault implies kernel mode so its failure (for some reason) can reuse the @no_context label and we can remove @bad_area_nosemaphore.

Reproduce user test for original problem:

------------------------>8----------------- #include <stdlib.h> #include <stdint.h>

int main(int argc, char *argv[]) { volatile uint32_t temp;

temp = *(uint32_t *)(0x70000000); } ------------------------>8-----------------

Cc: stable@vger.kernel.org Signed-off-by: Eugeniy Paltsev Eugeniy.Paltsev@synopsys.com Signed-off-by: Vineet Gupta vgupta@synopsys.com --- arch/arc/mm/fault.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index 8df1638259f3..6836095251ed 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -66,7 +66,7 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) struct vm_area_struct *vma = NULL; struct task_struct *tsk = current; struct mm_struct *mm = tsk->mm; - int si_code = 0; + int si_code = SEGV_MAPERR; int ret; vm_fault_t fault; int write = regs->ecr_cause & ECR_C_PROTV_STORE; /* ST/EX */ @@ -81,16 +81,14 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) * only copy the information from the master page table, * nothing more. */ - if (address >= VMALLOC_START) { + if (address >= VMALLOC_START && !user_mode(regs)) { ret = handle_kernel_vaddr_fault(address); if (unlikely(ret)) - goto bad_area_nosemaphore; + goto no_context; else return; }

- si_code = SEGV_MAPERR; - /* * If we're in an interrupt or have no user * context, we must not take the fault.. @@ -198,7 +196,6 @@ void do_page_fault(unsigned long address, struct pt_regs *regs) bad_area: up_read(&mm->mmap_sem);

-bad_area_nosemaphore: /* User mode accesses just cause a SIGSEGV */ if (user_mode(regs)) { tsk->thread.fault_address = address;