Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933562AbdCWMmY (ORCPT ); Thu, 23 Mar 2017 08:42:24 -0400 Received: from foss.arm.com ([217.140.101.70]:55778 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932249AbdCWMmW (ORCPT ); Thu, 23 Mar 2017 08:42:22 -0400 Date: Thu, 23 Mar 2017 12:41:54 +0000 From: Mark Rutland To: Andrey Ryabinin Cc: Andrew Morton , Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] kasan: report only the first error by default Message-ID: <20170323124154.GE9287@leverpostej> References: <20170322160647.32032-1-aryabinin@virtuozzo.com> <20170323114916.29871-1-aryabinin@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170323114916.29871-1-aryabinin@virtuozzo.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4434 Lines: 168 On Thu, Mar 23, 2017 at 02:49:16PM +0300, Andrey Ryabinin wrote: > + kasan_multi_shot > + [KNL] Enforce KASAN (Kernel Address Sanitizer) to print > + report on every invalid memory access. Without this > + parameter KASAN will print report only for the first > + invalid access. > + The option looks fine to me. > static int __init kmalloc_tests_init(void) > { > + /* Rise reports limit high enough to see all the following bugs */ > + atomic_add(100, &kasan_report_count); > + > + /* > + * kasan is unreliable now, disable reports if > + * we are in single shot mode > + */ > + atomic_sub(100, &kasan_report_count); > return -EAGAIN; > } ... but these magic numbers look rather messy. [...] > +atomic_t kasan_report_count = ATOMIC_INIT(1); > +EXPORT_SYMBOL_GPL(kasan_report_count); > + > +static int __init kasan_set_multi_shot(char *str) > +{ > + atomic_set(&kasan_report_count, 1000000000); > + return 1; > +} > +__setup("kasan_multi_shot", kasan_set_multi_shot); ... likewise. Rather than trying to pick an arbitrarily large number, how about we use separate flags to determine whether we're in multi-shot mode, and whether a (oneshot) report has been made. How about the below? Thanks, Mark. ---->8---- diff --git a/include/linux/kasan.h b/include/linux/kasan.h index ceb3fe7..291d7b3 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -74,6 +74,9 @@ struct kasan_cache { static inline void kasan_unpoison_slab(const void *ptr) { ksize(ptr); } size_t kasan_metadata_size(struct kmem_cache *cache); +bool kasan_save_enable_multi_shot(void); +void kasan_restore_multi_shot(bool enabled); + #else /* CONFIG_KASAN */ static inline void kasan_unpoison_shadow(const void *address, size_t size) {} diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 0b1d314..ae59dc2 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -12,6 +12,7 @@ #define pr_fmt(fmt) "kasan test: %s " fmt, __func__ #include +#include #include #include #include @@ -474,6 +475,12 @@ static noinline void __init use_after_scope_test(void) static int __init kmalloc_tests_init(void) { + /* + * Temporarily enable multi-shot mode. Otherwise, we'd only get a + * report for the first case. + */ + bool multishot = kasan_save_enable_multi_shot(); + kmalloc_oob_right(); kmalloc_oob_left(); kmalloc_node_oob_right(); @@ -499,6 +506,9 @@ static int __init kmalloc_tests_init(void) ksize_unpoisons_memory(); copy_user_test(); use_after_scope_test(); + + kasan_restore_multi_shot(multishot); + return -EAGAIN; } diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index 1c260e6..dd2dea8 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -96,11 +96,6 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr) << KASAN_SHADOW_SCALE_SHIFT); } -static inline bool kasan_report_enabled(void) -{ - return !current->kasan_depth; -} - void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip); void kasan_report_double_free(struct kmem_cache *cache, void *object, diff --git a/mm/kasan/report.c b/mm/kasan/report.c index f479365..f1c5892 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -13,6 +13,7 @@ * */ +#include #include #include #include @@ -293,6 +294,40 @@ static void kasan_report_error(struct kasan_access_info *info) kasan_end_report(&flags); } +static unsigned long kasan_flags; + +#define KASAN_BIT_REPORTED 0 +#define KASAN_BIT_MULTI_SHOT 1 + +bool kasan_save_enable_multi_shot(void) +{ + return test_and_set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); +} +EXPORT_SYMBOL_GPL(kasan_save_enable_multi_shot); + +void kasan_restore_multi_shot(bool enabled) +{ + if (!enabled) + clear_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); +} +EXPORT_SYMBOL_GPL(kasan_restore_multi_shot); + +static int __init kasan_set_multi_shot(char *str) +{ + set_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags); + return 1; +} +__setup("kasan_multi_shot", kasan_set_multi_shot); + +static inline bool kasan_report_enabled(void) +{ + if (current->kasan_depth) + return false; + if (test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) + return true; + return !test_and_set_bit(KASAN_BIT_REPORTED, &kasan_flags); +} + void kasan_report(unsigned long addr, size_t size, bool is_write, unsigned long ip) {