From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752242Ab3KBMSu (ORCPT ); Sat, 2 Nov 2013 08:18:50 -0400 Received: from us01smtp2.synopsys.com ([198.182.44.80]:41451 "EHLO kiruna.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751942Ab3KBMSs (ORCPT ); Sat, 2 Nov 2013 08:18:48 -0400 From: Vineet Gupta To: Linus Torvalds CC: lkml , Gilad Ben-Yossef , Noam Camus , Peter Hurley , Vineet Gupta , Subject: [PATCH] ARC: Incorrect mm reference used in vmalloc fault handler Date: Sat, 2 Nov 2013 17:47:49 +0530 Message-ID: <1383394669-20175-2-git-send-email-vgupta@synopsys.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1383394669-20175-1-git-send-email-vgupta@synopsys.com> References: <1383394669-20175-1-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.12.197.76] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: linux-kernel@vger.kernel.org --- arch/arc/mm/fault.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c index 81554ded1260..9c69552350c4 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(unsigned long address, struct pt_regs *regs) * 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 -- 1.8.1.2