diff options
authorAndrey Konovalov <andreyknvl@google.com>2020-12-10 15:42:14 +1100
committerStephen Rothwell <sfr@canb.auug.org.au>2020-12-16 18:03:01 +1100
commite565f05850f1b54c62fa9a000d77e9570beb58d1 (patch)
parent52931fca5ba8a7b82e5f7d3576b2ed13904b744f (diff)
kasan: simplify quarantine_put call site
Patch series "kasan: boot parameters for hardware tag-based mode", v4. === Overview Hardware tag-based KASAN mode [1] is intended to eventually be used in production as a security mitigation. Therefore there's a need for finer control over KASAN features and for an existence of a kill switch. This patchset adds a few boot parameters for hardware tag-based KASAN that allow to disable or otherwise control particular KASAN features, as well as provides some initial optimizations for running KASAN in production. There's another planned patchset what will further optimize hardware tag-based KASAN, provide proper benchmarking and tests, and will fully enable tag-based KASAN for production use. Hardware tag-based KASAN relies on arm64 Memory Tagging Extension (MTE) [2] to perform memory and pointer tagging. Please see [3] and [4] for detailed analysis of how MTE helps to fight memory safety problems. The features that can be controlled are: 1. Whether KASAN is enabled at all. 2. Whether KASAN collects and saves alloc/free stacks. 3. Whether KASAN panics on a detected bug or not. The patch titled "kasan: add and integrate kasan boot parameters" of this series adds a few new boot parameters. kasan.mode allows to choose one of three main modes: - kasan.mode=off - KASAN is disabled, no tag checks are performed - kasan.mode=prod - only essential production features are enabled - kasan.mode=full - all KASAN features are enabled The chosen mode provides default control values for the features mentioned above. However it's also possible to override the default values by providing: - kasan.stacktrace=off/on - enable stacks collection (default: on for mode=full, otherwise off) - kasan.fault=report/panic - only report tag fault or also panic (default: report) If kasan.mode parameter is not provided, it defaults to full when CONFIG_DEBUG_KERNEL is enabled, and to prod otherwise. It is essential that switching between these modes doesn't require rebuilding the kernel with different configs, as this is required by the Android GKI (Generic Kernel Image) initiative. === Benchmarks For now I've only performed a few simple benchmarks such as measuring kernel boot time and slab memory usage after boot. There's an upcoming patchset which will optimize KASAN further and include more detailed benchmarking results. The benchmarks were performed in QEMU and the results below exclude the slowdown caused by QEMU memory tagging emulation (as it's different from the slowdown that will be introduced by hardware and is therefore irrelevant). KASAN_HW_TAGS=y + kasan.mode=off introduces no performance or memory impact compared to KASAN_HW_TAGS=n. kasan.mode=prod (manually excluding tagging) introduces 3% of performance and no memory impact (except memory used by hardware to store tags) compared to kasan.mode=off. kasan.mode=full has about 40% performance and 30% memory impact over kasan.mode=prod. Both come from alloc/free stack collection. === Notes This patchset is available here: https://github.com/xairy/linux/tree/up-boot-mte-v4 This patchset is based on v11 of "kasan: add hardware tag-based mode for arm64" patchset [1]. For testing in QEMU hardware tag-based KASAN requires: 1. QEMU built from master [6] (use "-machine virt,mte=on -cpu max" arguments to run). 2. GCC version 10. [1] https://lore.kernel.org/linux-arm-kernel/cover.1606161801.git.andreyknvl@google.com/T/#t [2] https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/posts/enhancing-memory-safety [3] https://arxiv.org/pdf/1802.09517.pdf [4] https://github.com/microsoft/MSRC-Security-Research/blob/master/papers/2020/Security%20analysis%20of%20memory%20tagging.pdf [5] https://source.android.com/devices/architecture/kernel/generic-kernel-image [6] https://github.com/qemu/qemu === Tags Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> This patch (of 19): Move get_free_info() call into quarantine_put() to simplify the call site. No functional changes. Link: https://lkml.kernel.org/r/cover.1606162397.git.andreyknvl@google.com Link: https://lkml.kernel.org/r/312d0a3ef92cc6dc4fa5452cbc1714f9393ca239.1606162397.git.andreyknvl@google.com Link: https://linux-review.googlesource.com/id/Iab0f04e7ebf8d83247024b7190c67c3c34c7940f Signed-off-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Marco Elver <elver@google.com> Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> Cc: Alexander Potapenko <glider@google.com> Cc: Evgenii Stepanov <eugenis@google.com> Cc: Branislav Rankov <Branislav.Rankov@arm.com> Cc: Kevin Brodsky <kevin.brodsky@arm.com> Cc: Vasily Gorbik <gor@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
3 files changed, 5 insertions, 5 deletions
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 998aede4d172..e11fac2ee30c 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -317,7 +317,7 @@ static bool __kasan_slab_free(struct kmem_cache *cache, void *object,
kasan_set_free_info(cache, object, tag);
- quarantine_put(get_free_info(cache, object), cache);
+ quarantine_put(cache, object);
diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
index 64560cc71191..13c511e85d5f 100644
--- a/mm/kasan/kasan.h
+++ b/mm/kasan/kasan.h
@@ -216,12 +216,11 @@ struct kasan_track *kasan_get_free_track(struct kmem_cache *cache,
#if defined(CONFIG_KASAN_GENERIC) && \
(defined(CONFIG_SLAB) || defined(CONFIG_SLUB))
-void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache);
+void quarantine_put(struct kmem_cache *cache, void *object);
void quarantine_reduce(void);
void quarantine_remove_cache(struct kmem_cache *cache);
-static inline void quarantine_put(struct kasan_free_meta *info,
- struct kmem_cache *cache) { }
+static inline void quarantine_put(struct kmem_cache *cache, void *object) { }
static inline void quarantine_reduce(void) { }
static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 693b05e2c2aa..88fab9ff2d6e 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -163,11 +163,12 @@ static void qlist_free_all(struct qlist_head *q, struct kmem_cache *cache)
-void quarantine_put(struct kasan_free_meta *info, struct kmem_cache *cache)
+void quarantine_put(struct kmem_cache *cache, void *object)
unsigned long flags;
struct qlist_head *q;
struct qlist_head temp = QLIST_INIT;
+ struct kasan_free_meta *info = get_free_info(cache, object);
* Note: irq must be disabled until after we move the batch to the