From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754767AbbFCPnK (ORCPT ); Wed, 3 Jun 2015 11:43:10 -0400 Received: from foss.arm.com ([217.140.101.70]:39928 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753591AbbFCPnF (ORCPT ); Wed, 3 Jun 2015 11:43:05 -0400 From: Catalin Marinas To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Vignesh Radhakrishnan , Andrew Morton Subject: [PATCH] mm: kmemleak: Fix crashing during kmemleak disabling Date: Wed, 3 Jun 2015 16:42:56 +0100 Message-Id: <1433346176-912-1-git-send-email-catalin.marinas@arm.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the current implementation, if kmemleak is disabled because of an error condition (e.g. fails to allocate metadata), alloc/free calls are no longer tracked. Usually this is not a problem since the kmemleak metadata is being removed via kmemleak_do_cleanup(). However, if the scanning thread is running at the time of disabling, kmemleak would no longer notice a potential vfree() call and the freed/unmapped object may still be accessed, causing a fault. This patch separates the kmemleak_free() enabling/disabling from the overall kmemleak_enabled nob so that we can defer the disabling of the object freeing tracking until the scanning thread completed. The kmemleak_free_part() is deliberately ignored by this patch since this is only called during boot before the scanning thread started. Signed-off-by: Catalin Marinas Reported-by: Vignesh Radhakrishnan Tested-by: Vignesh Radhakrishnan Cc: Andrew Morton Cc: --- mm/kmemleak.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index f0fe4f2c1fa7..11d6f8015896 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -195,6 +195,8 @@ static struct kmem_cache *scan_area_cache; /* set if tracing memory operations is enabled */ static int kmemleak_enabled; +/* same as above but only for the kmemleak_free() callback */ +static int kmemleak_free_enabled; /* set in the late_initcall if there were no errors */ static int kmemleak_initialized; /* enables or disables early logging of the memory operations */ @@ -942,7 +944,7 @@ void __ref kmemleak_free(const void *ptr) { pr_debug("%s(0x%p)\n", __func__, ptr); - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) + if (kmemleak_free_enabled && ptr && !IS_ERR(ptr)) delete_object_full((unsigned long)ptr); else if (kmemleak_early_log) log_early(KMEMLEAK_FREE, ptr, 0, 0); @@ -982,7 +984,7 @@ void __ref kmemleak_free_percpu(const void __percpu *ptr) pr_debug("%s(0x%p)\n", __func__, ptr); - if (kmemleak_enabled && ptr && !IS_ERR(ptr)) + if (kmemleak_free_enabled && ptr && !IS_ERR(ptr)) for_each_possible_cpu(cpu) delete_object_full((unsigned long)per_cpu_ptr(ptr, cpu)); @@ -1750,6 +1752,12 @@ static void kmemleak_do_cleanup(struct work_struct *work) mutex_lock(&scan_mutex); stop_scan_thread(); + /* + * Once the scan thread has stopped, it is safe to no longer track + * object freeing. + */ + kmemleak_free_enabled = 0; + if (!kmemleak_found_leaks) __kmemleak_do_cleanup(); else @@ -1776,6 +1784,8 @@ static void kmemleak_disable(void) /* check whether it is too early for a kernel thread */ if (kmemleak_initialized) schedule_work(&cleanup_work); + else + kmemleak_free_enabled = 0; pr_info("Kernel memory leak detector disabled\n"); } @@ -1840,8 +1850,10 @@ void __init kmemleak_init(void) if (kmemleak_error) { local_irq_restore(flags); return; - } else + } else { kmemleak_enabled = 1; + kmemleak_free_enabled = 1; + } local_irq_restore(flags); /*