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Tue, 21 Sep 2021 03:50:15 -0700 (PDT) MIME-Version: 1.0 References: <20210921101014.1938382-1-elver@google.com> <20210921101014.1938382-3-elver@google.com> In-Reply-To: <20210921101014.1938382-3-elver@google.com> From: Dmitry Vyukov Date: Tue, 21 Sep 2021 12:50:04 +0200 Message-ID: Subject: Re: [PATCH v2 3/5] kfence: move saving stack trace of allocations into __kfence_alloc() To: Marco Elver Cc: Andrew Morton , Alexander Potapenko , Jann Horn , Aleksandr Nogikh , Taras Madan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=pGybIBE1; spf=pass (imf10.hostedemail.com: domain of dvyukov@google.com designates 209.85.161.44 as permitted sender) smtp.mailfrom=dvyukov@google.com; dmarc=pass (policy=reject) header.from=google.com X-Stat-Signature: dz77wjhfawqzr73fph58y4q8yn5xo69x X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 5C4F96001982 X-HE-Tag: 1632221416-244581 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: On Tue, 21 Sept 2021 at 12:10, 'Marco Elver' via kasan-dev wrote: > > Move the saving of the stack trace of allocations into __kfence_alloc(), > so that the stack entries array can be used outside of > kfence_guarded_alloc() and we avoid potentially unwinding the stack > multiple times. > > Signed-off-by: Marco Elver Reviewed-by: Dmitry Vyukov > --- > v2: > * New patch. > --- > mm/kfence/core.c | 35 ++++++++++++++++++++++++----------- > 1 file changed, 24 insertions(+), 11 deletions(-) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 249d75b7e5ee..db01814f8ff0 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -187,19 +187,26 @@ static inline unsigned long metadata_to_pageaddr(const struct kfence_metadata *m > * Update the object's metadata state, including updating the alloc/free stacks > * depending on the state transition. > */ > -static noinline void metadata_update_state(struct kfence_metadata *meta, > - enum kfence_object_state next) > +static noinline void > +metadata_update_state(struct kfence_metadata *meta, enum kfence_object_state next, > + unsigned long *stack_entries, size_t num_stack_entries) > { > struct kfence_track *track = > next == KFENCE_OBJECT_FREED ? &meta->free_track : &meta->alloc_track; > > lockdep_assert_held(&meta->lock); > > - /* > - * Skip over 1 (this) functions; noinline ensures we do not accidentally > - * skip over the caller by never inlining. > - */ > - track->num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1); > + if (stack_entries) { > + memcpy(track->stack_entries, stack_entries, > + num_stack_entries * sizeof(stack_entries[0])); > + } else { > + /* > + * Skip over 1 (this) functions; noinline ensures we do not > + * accidentally skip over the caller by never inlining. > + */ > + num_stack_entries = stack_trace_save(track->stack_entries, KFENCE_STACK_DEPTH, 1); > + } > + track->num_stack_entries = num_stack_entries; > track->pid = task_pid_nr(current); > track->cpu = raw_smp_processor_id(); > track->ts_nsec = local_clock(); /* Same source as printk timestamps. */ > @@ -261,7 +268,8 @@ static __always_inline void for_each_canary(const struct kfence_metadata *meta, > } > } > > -static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp) > +static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t gfp, > + unsigned long *stack_entries, size_t num_stack_entries) > { > struct kfence_metadata *meta = NULL; > unsigned long flags; > @@ -320,7 +328,7 @@ static void *kfence_guarded_alloc(struct kmem_cache *cache, size_t size, gfp_t g > addr = (void *)meta->addr; > > /* Update remaining metadata. */ > - metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED); > + metadata_update_state(meta, KFENCE_OBJECT_ALLOCATED, stack_entries, num_stack_entries); > /* Pairs with READ_ONCE() in kfence_shutdown_cache(). */ > WRITE_ONCE(meta->cache, cache); > meta->size = size; > @@ -400,7 +408,7 @@ static void kfence_guarded_free(void *addr, struct kfence_metadata *meta, bool z > memzero_explicit(addr, meta->size); > > /* Mark the object as freed. */ > - metadata_update_state(meta, KFENCE_OBJECT_FREED); > + metadata_update_state(meta, KFENCE_OBJECT_FREED, NULL, 0); > > raw_spin_unlock_irqrestore(&meta->lock, flags); > > @@ -742,6 +750,9 @@ void kfence_shutdown_cache(struct kmem_cache *s) > > void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) > { > + unsigned long stack_entries[KFENCE_STACK_DEPTH]; > + size_t num_stack_entries; > + > /* > * Perform size check before switching kfence_allocation_gate, so that > * we don't disable KFENCE without making an allocation. > @@ -786,7 +797,9 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) > if (!READ_ONCE(kfence_enabled)) > return NULL; > > - return kfence_guarded_alloc(s, size, flags); > + num_stack_entries = stack_trace_save(stack_entries, KFENCE_STACK_DEPTH, 0); > + > + return kfence_guarded_alloc(s, size, flags, stack_entries, num_stack_entries); > } > > size_t kfence_ksize(const void *addr) > -- > 2.33.0.464.g1972c5931b-goog > > -- > You received this message because you are subscribed to the Google Groups "kasan-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/20210921101014.1938382-3-elver%40google.com.