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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=ISHwxx5EnSKzUDUjZ1ysUZFyHBfF802klWxWhYA/428=; b=Sqz/IIZMqS7xNsmfx6fP4HX/y5rz+YmH/i89XPH0gEl6EUqH6V5KhUQXCxsj/MFkB7 eWJenk0dqYCCBMv9zDPoOsrLAR7le3JgEmv/Kxqkf5NDDHeLYKUui3iE+TUD92mcyj7P sDxrG5vBK0vXtlqS1vBsWoC3p/VwOBOsEsGA01AdXb6wmNSYWd0nS9U7iCt77mqf3qtg GL2RdXqrl/YYWMW03G/yTGK7hGlNvrhmaZxZqH7rEzZEJs0nYBlS+H3RYd64jd9ngbKi q0UsaTHJ+EJz8kkT637ejvS/Q2TN1d3j314kEKaDhzRO8pR5sVIt0efKlhNLh7v4fUTU CwTQ== X-Gm-Message-State: AOAM5301aKCY324XppeWLHXR+23+qXmKVRtQ1VfMg1grSkY5BzYDkjgB mBVluCJVoxh7Qa5iuZVZNbgOM87cN1bwqKYA X-Google-Smtp-Source: ABdhPJxP6vMDfthzecVC5ecdLO+5Dv7Y8pBeoXM66UJWgdoywOg+JFnFIENVMygIhQfAgTki+HWSylKOMpIDzaAZ X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:edb8:b79c:2e20:e531]) (user=andreyknvl job=sendgmr) by 2002:a7b:c5c1:: with SMTP id n1mr4107578wmk.163.1612539577356; Fri, 05 Feb 2021 07:39:37 -0800 (PST) Date: Fri, 5 Feb 2021 16:39:09 +0100 In-Reply-To: Message-Id: <1cf400f36ab1fd3c83e7626c3797cb11ebf9ef7f.1612538932.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH v2 08/12] kasan, mm: optimize krealloc poisoning From: Andrey Konovalov To: Andrew Morton , Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Marco Elver X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210205_103941_017489_DEAFCEA2 X-CRM114-Status: GOOD ( 20.43 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Branislav Rankov , Andrey Konovalov , Kevin Brodsky , Will Deacon , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Currently, krealloc() always calls ksize(), which unpoisons the whole object including the redzone. This is inefficient, as kasan_krealloc() repoisons the redzone for objects that fit into the same buffer. This patch changes krealloc() instrumentation to use uninstrumented __ksize() that doesn't unpoison the memory. Instead, kasan_kreallos() is changed to unpoison the memory excluding the redzone. For objects that don't fit into the old allocation, this patch disables KASAN accessibility checks when copying memory into a new object instead of unpoisoning it. Signed-off-by: Andrey Konovalov --- mm/kasan/common.c | 12 ++++++++++-- mm/slab_common.c | 20 ++++++++++++++------ 2 files changed, 24 insertions(+), 8 deletions(-) diff --git a/mm/kasan/common.c b/mm/kasan/common.c index 7ea643f7e69c..a8a67dca5e55 100644 --- a/mm/kasan/common.c +++ b/mm/kasan/common.c @@ -476,7 +476,7 @@ static void *____kasan_kmalloc(struct kmem_cache *cache, const void *object, /* * The object has already been unpoisoned by kasan_slab_alloc() for - * kmalloc() or by ksize() for krealloc(). + * kmalloc() or by kasan_krealloc() for krealloc(). */ /* @@ -526,7 +526,7 @@ void * __must_check __kasan_kmalloc_large(const void *ptr, size_t size, /* * The object has already been unpoisoned by kasan_alloc_pages() for - * alloc_pages() or by ksize() for krealloc(). + * alloc_pages() or by kasan_krealloc() for krealloc(). */ /* @@ -554,8 +554,16 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag if (unlikely(object == ZERO_SIZE_PTR)) return (void *)object; + /* + * Unpoison the object's data. + * Part of it might already have been unpoisoned, but it's unknown + * how big that part is. + */ + kasan_unpoison(object, size); + page = virt_to_head_page(object); + /* Piggy-back on kmalloc() instrumentation to poison the redzone. */ if (unlikely(!PageSlab(page))) return __kasan_kmalloc_large(object, size, flags); else diff --git a/mm/slab_common.c b/mm/slab_common.c index dad70239b54c..60a2f49df6ce 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1140,19 +1140,27 @@ static __always_inline void *__do_krealloc(const void *p, size_t new_size, void *ret; size_t ks; - if (likely(!ZERO_OR_NULL_PTR(p)) && !kasan_check_byte(p)) - return NULL; - - ks = ksize(p); + /* Don't use instrumented ksize to allow precise KASAN poisoning. */ + if (likely(!ZERO_OR_NULL_PTR(p))) { + if (!kasan_check_byte(p)) + return NULL; + ks = kfence_ksize(p) ?: __ksize(p); + } else + ks = 0; + /* If the object still fits, repoison it precisely. */ if (ks >= new_size) { p = kasan_krealloc((void *)p, new_size, flags); return (void *)p; } ret = kmalloc_track_caller(new_size, flags); - if (ret && p) - memcpy(ret, p, ks); + if (ret && p) { + /* Disable KASAN checks as the object's redzone is accessed. */ + kasan_disable_current(); + memcpy(ret, kasan_reset_tag(p), ks); + kasan_enable_current(); + } return ret; }