From: Vineet Gupta Date: Sat, 2 Nov 2013 12:17:49 +0000 (+0530) Subject: ARC: Incorrect mm reference used in vmalloc fault handler X-Git-Tag: firefly_0821_release~176^2~5067 X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=9c41f4eeb9d51f3ece20428d35a3ea32cf3b5622;p=firefly-linux-kernel-4.4.55.git ARC: Incorrect mm reference used in vmalloc fault handler A vmalloc fault needs to sync up PGD/PTE entry from init_mm to current task's "active_mm". ARC vmalloc fault handler however was using mm. A vmalloc fault for non user task context (actually pre-userland, from init thread's open for /dev/console) caused the handler to deref NULL mm (for mm->pgd) The reasons it worked so far is amazing: 1. By default (!SMP), vmalloc fault handler uses a cached value of PGD. In SMP that MMU register is repurposed hence need for mm pointer deref. 2. In pre-3.12 SMP kernel, the problem triggering vmalloc didn't exist in pre-userland code path - it was introduced with commit 20bafb3d23d108bc "n_tty: Move buffers into n_tty_data" Signed-off-by: Vineet Gupta Cc: Gilad Ben-Yossef Cc: Noam Camus Cc: stable@vger.kernel.org #3.10 and 3.11 Cc: Peter Hurley Signed-off-by: Linus Torvalds --- diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index d63f3de0cd5b..0c14d8a52683 100644 --- a/arch/arc/mm/fault.c +++ b/arch/arc/mm/fault.c @@ -17,7 +17,7 @@ #include #include -static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) +static int handle_vmalloc_fault(unsigned long address) { /* * Synchronize this task's top level page-table @@ -27,7 +27,7 @@ static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address) pud_t *pud, *pud_k; pmd_t *pmd, *pmd_k; - pgd = pgd_offset_fast(mm, address); + pgd = pgd_offset_fast(current->active_mm, address); pgd_k = pgd_offset_k(address); if (!pgd_present(*pgd_k)) @@ -72,7 +72,7 @@ void do_page_fault(struct pt_regs *regs, unsigned long address) * nothing more. */ if (address >= VMALLOC_START && address <= VMALLOC_END) { - ret = handle_vmalloc_fault(mm, address); + ret = handle_vmalloc_fault(address); if (unlikely(ret)) goto bad_area_nosemaphore; else