From e8a4efd041734c248674f585d44b770ef8ea79aa Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Fri, 31 Mar 2017 15:12:04 -0700 Subject: [PATCH] BACKPORT: kasan: report only the first error by default Disable kasan after the first report. There are several reasons for this: - Single bug quite often has multiple invalid memory accesses causing storm in the dmesg. - Write OOB access might corrupt metadata so the next report will print bogus alloc/free stacktraces. - Reports after the first easily could be not bugs by itself but just side effects of the first one. Given that multiple reports usually only do harm, it makes sense to disable kasan after the first one. If user wants to see all the reports, the boot-time parameter kasan_multi_shot must be used. [aryabinin@virtuozzo.com: wrote changelog and doc, added missing include] Link: http://lkml.kernel.org/r/20170323154416.30257-1-aryabinin@virtuozzo.com Signed-off-by: Mark Rutland Signed-off-by: Andrey Ryabinin Cc: Andrey Konovalov Cc: Alexander Potapenko Cc: Dmitry Vyukov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Bug: 64145065 (cherry-picked from b0845ce58379d11dcad4cdb6824a6410de260216) Change-Id: Ia8c6d40dd0d4f5b944bf3501c08d7a825070b116 Signed-off-by: Paul Lawrence --- include/linux/kasan.h | 3 +++ lib/test_kasan.c | 10 ++++++++++ mm/kasan/kasan.h | 5 ----- mm/kasan/report.c | 36 ++++++++++++++++++++++++++++++++++++ 4 files changed, 49 insertions(+), 5 deletions(-) diff --git a/include/linux/kasan.h b/include/linux/kasan.h index 7793036eac80..b37afd197eed 100644 --- a/include/linux/kasan.h +++ b/include/linux/kasan.h @@ -75,6 +75,9 @@ size_t ksize(const void *); 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 fbdf87920093..0e70ecc12fe2 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -19,6 +19,7 @@ #include #include #include +#include /* * Note: test functions are marked noinline so that their names appear in @@ -441,6 +442,12 @@ 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(); @@ -465,6 +472,9 @@ 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 1c260e6b3b3c..dd2dea8eb077 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 f479365530b6..ab42a0803f16 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -13,7 +13,9 @@ * */ +#include #include +#include #include #include #include @@ -293,6 +295,40 @@ 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) {