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Thu, 25 Jan 2024 01:48:23 -0800 (PST) Date: Thu, 25 Jan 2024 10:47:43 +0100 In-Reply-To: <20240125094815.2041933-1-elver@google.com> Mime-Version: 1.0 References: <20240125094815.2041933-1-elver@google.com> X-Mailer: git-send-email 2.43.0.429.g432eaa2c6b-goog Message-ID: <20240125094815.2041933-2-elver@google.com> Subject: [PATCH 2/2] kasan: revert eviction of stack traces in generic mode From: Marco Elver To: elver@google.com, Andrew Morton Cc: Andrey Konovalov , Alexander Potapenko , Dmitry Vyukov , Vlastimil Babka , Andrey Ryabinin , Vincenzo Frascino , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 97A8A40019 X-Stat-Signature: dimbsckxh13t4w5xzzw9cht3s37ioz1a X-HE-Tag: 1706176104-203413 X-HE-Meta: U2FsdGVkX19TBlq65YCE1AH/1YvYM4EI+cpYEaGk5OVxDXTDZX2qBQw3vVdKnHhVbDIBYGfi0NP89w2O7O5Nwg6EOzhFrOlXu6ITOIQgOZGP4EsuEYY3SyqEaYU8wcr+87PgpU3zFYdHKKTNoOwFJA3fn+nMKoLkO6fi1Kp4v5LjeC39/owyNgi61WwfDAg5cAvTAAzh7LVMAKIKphkIvsupT22qpNmjxI8V+nQJyB70lnWyPX50AH77UFUup5QF49EeaYelVpbKgdRjungoc4c/jeD71pJCy2uSf4dWKdrqvcyjQS/3EqH9MjltPlAWc4NaRY5es3cIrbt4Zm5+ly4CWoNsNjzCH88cyZB7K9KUARkAiR5TOZl/lO65iSrlbB2m9EuNDd8jUSIViGE18Q4z12GPM0puiaUUoqjmu6WAkNPqYiUPJiBg3DE2QLnN8X2Y5yWt+/NJEEKmiWgv/DZkm0WaLzuRCzIsotyBFQIXdJS3/qCFYS+UTYDKfvqJ5kIUrFs+vE6xQcnu7e4nWRlvbCMUFbr3zz8bTSu9SNuGn2vvg2nWRZsTqYUzczoTBBcqUlWXxJ/cCttzojUx7iEhvFpj0bFquIXPsv0/HjdM5HnwsuH/g2spZQA4dgQz22aFqG6uGO8/Kkl1bKy5JyWPkVoRrlbwi8FN7WlO0WowNwcvtMZtjn2sI9tDbZbU2ObJRvq2zsujhqOjBMqJu5CZY2xh6SlV3VSGUcTlh2A/KHQ/HQH22qcyFxJK/GE8ko5d6935V2J7ClFwk5fSEyh3feD4ckT+NZX84RN5RRBl7HGpN7+Ggc1CkMmfGvgBfAk6cEY+AHmmFt+d+s+p9LeprrwmmpGcINMrPZtZisMPLC1yhkPpxJ0xisyfn/rZ+UfGBjSUVyJcTWklXcNYlhUzYQYOhOqlVmK3HVifEGu+TewomiZqFrnIMnc9OaCrDTTufUaWQUp7/rh+V/p UWEH0z5n 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: This partially reverts commits cc478e0b6bdf, 63b85ac56a64, 08d7c94d9635, a414d4286f34, and 773688a6cb24 to make use of variable-sized stack depot records, since eviction of stack entries from stack depot forces fixed- sized stack records. Care was taken to retain the code cleanups by the above commits. Eviction was added to generic KASAN as a response to alleviating the additional memory usage from fixed-sized stack records, but this still uses more memory than previously. With the re-introduction of variable-sized records for stack depot, we can just switch back to non-evictable stack records again, and return back to the previous performance and memory usage baseline. Before (observed after a KASAN kernel boot): pools: 597 allocations: 29657 frees: 6425 in_use: 23232 freelist_size: 3493 After: pools: 315 allocations: 28964 frees: 0 in_use: 28964 freelist_size: 0 As can be seen from the number of "frees", with a generic KASAN config, evictions are no longer used but due to using variable-sized records, I observe a reduction of 282 stack depot pools (saving 4512 KiB) with my test setup. Fixes: cc478e0b6bdf ("kasan: avoid resetting aux_lock") Fixes: 63b85ac56a64 ("kasan: stop leaking stack trace handles") Fixes: 08d7c94d9635 ("kasan: memset free track in qlink_free") Fixes: a414d4286f34 ("kasan: handle concurrent kasan_record_aux_stack calls") Fixes: 773688a6cb24 ("kasan: use stack_depot_put for Generic mode") Signed-off-by: Marco Elver Cc: Alexander Potapenko Cc: Andrey Konovalov Cc: Dmitry Vyukov Reviewed-by: Andrey Konovalov --- mm/kasan/common.c | 3 +-- mm/kasan/generic.c | 54 ++++++---------------------------------------- mm/kasan/kasan.h | 8 ------- 3 files changed, 8 insertions(+), 57 deletions(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 610efae91220..ad32803e34e9 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -65,8 +65,7 @@ void kasan_save_track(struct kasan_track *track, gfp_t flags) { depot_stack_handle_t stack; - stack = kasan_save_stack(flags, - STACK_DEPOT_FLAG_CAN_ALLOC | STACK_DEPOT_FLAG_GET); + stack = kasan_save_stack(flags, STACK_DEPOT_FLAG_CAN_ALLOC); kasan_set_track(track, stack); } diff --git a/mm/kasan/generic.c b/mm/kasan/generic.c index df6627f62402..8bfb52b28c22 100644 --- a/mm/kasan/generic.c +++ b/mm/kasan/generic.c @@ -485,16 +485,6 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object) if (alloc_meta) { /* Zero out alloc meta to mark it as invalid. */ __memset(alloc_meta, 0, sizeof(*alloc_meta)); - - /* - * Prepare the lock for saving auxiliary stack traces. - * Temporarily disable KASAN bug reporting to allow instrumented - * raw_spin_lock_init to access aux_lock, which resides inside - * of a redzone. - */ - kasan_disable_current(); - raw_spin_lock_init(&alloc_meta->aux_lock); - kasan_enable_current(); } /* @@ -506,18 +496,8 @@ void kasan_init_object_meta(struct kmem_cache *cache, const void *object) static void release_alloc_meta(struct kasan_alloc_meta *meta) { - /* Evict the stack traces from stack depot. */ - stack_depot_put(meta->alloc_track.stack); - stack_depot_put(meta->aux_stack[0]); - stack_depot_put(meta->aux_stack[1]); - - /* - * Zero out alloc meta to mark it as invalid but keep aux_lock - * initialized to avoid having to reinitialize it when another object - * is allocated in the same slot. - */ - __memset(&meta->alloc_track, 0, sizeof(meta->alloc_track)); - __memset(meta->aux_stack, 0, sizeof(meta->aux_stack)); + /* Zero out alloc meta to mark it as invalid. */ + __memset(meta, 0, sizeof(*meta)); } static void release_free_meta(const void *object, struct kasan_free_meta *meta) @@ -526,9 +506,6 @@ static void release_free_meta(const void *object, struct kasan_free_meta *meta) if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META) return; - /* Evict the stack trace from the stack depot. */ - stack_depot_put(meta->free_track.stack); - /* Mark free meta as invalid. */ *(u8 *)kasan_mem_to_shadow(object) = KASAN_SLAB_FREE; } @@ -571,8 +548,6 @@ static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags) struct kmem_cache *cache; struct kasan_alloc_meta *alloc_meta; void *object; - depot_stack_handle_t new_handle, old_handle; - unsigned long flags; if (is_kfence_address(addr) || !slab) return; @@ -583,33 +558,18 @@ static void __kasan_record_aux_stack(void *addr, depot_flags_t depot_flags) if (!alloc_meta) return; - new_handle = kasan_save_stack(0, depot_flags); - - /* - * Temporarily disable KASAN bug reporting to allow instrumented - * spinlock functions to access aux_lock, which resides inside of a - * redzone. - */ - kasan_disable_current(); - raw_spin_lock_irqsave(&alloc_meta->aux_lock, flags); - old_handle = alloc_meta->aux_stack[1]; alloc_meta->aux_stack[1] = alloc_meta->aux_stack[0]; - alloc_meta->aux_stack[0] = new_handle; - raw_spin_unlock_irqrestore(&alloc_meta->aux_lock, flags); - kasan_enable_current(); - - stack_depot_put(old_handle); + alloc_meta->aux_stack[0] = kasan_save_stack(0, depot_flags); } void kasan_record_aux_stack(void *addr) { - return __kasan_record_aux_stack(addr, - STACK_DEPOT_FLAG_CAN_ALLOC | STACK_DEPOT_FLAG_GET); + return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_CAN_ALLOC); } void kasan_record_aux_stack_noalloc(void *addr) { - return __kasan_record_aux_stack(addr, STACK_DEPOT_FLAG_GET); + return __kasan_record_aux_stack(addr, 0); } void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) @@ -620,7 +580,7 @@ void kasan_save_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags) if (!alloc_meta) return; - /* Evict previous stack traces (might exist for krealloc or mempool). */ + /* Invalidate previous stack traces (might exist for krealloc or mempool). */ release_alloc_meta(alloc_meta); kasan_save_track(&alloc_meta->alloc_track, flags); @@ -634,7 +594,7 @@ void kasan_save_free_info(struct kmem_cache *cache, void *object) if (!free_meta) return; - /* Evict previous stack trace (might exist for mempool). */ + /* Invalidate previous stack trace (might exist for mempool). */ release_free_meta(object, free_meta); kasan_save_track(&free_meta->free_track, 0); diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h index d0f172f2b978..216ae0ef1e4b 100644 --- a/mm/kasan/kasan.h +++ b/mm/kasan/kasan.h @@ -6,7 +6,6 @@ #include #include #include -#include #include #if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS) @@ -265,13 +264,6 @@ struct kasan_global { struct kasan_alloc_meta { struct kasan_track alloc_track; /* Free track is stored in kasan_free_meta. */ - /* - * aux_lock protects aux_stack from accesses from concurrent - * kasan_record_aux_stack calls. It is a raw spinlock to avoid sleeping - * on RT kernels, as kasan_record_aux_stack_noalloc can be called from - * non-sleepable contexts. - */ - raw_spinlock_t aux_lock; depot_stack_handle_t aux_stack[2]; };