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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=wTS7rGEWy/lmgEwVXVBE+5vzcvue/e9GmeYKwLI3/GI=; b=jUjCGlnk2IvgHw1n5mP+jTbEq34vHZLjmGEvLg24CcSFKIp5dMLO5Ln8+ZjzMdvyWm o0ZHo58G0Ui05LdoOIeM+egGguGGYGzDXiFoO5t/Sy+sW42EksgKW4mH1P14Rv0pDMPj I0bf3ZMPNn9f7xAe7kS7X5KJ4SEtVuF5EBv2Q2ez0sqdTLRQaAWWPGdhcICJ9ViUXwtC MbxQfyPK/1DeJ82EA0g7JnWIiCVgq9JvpDsWxzCUSZ1wzojA6+kvN2REw1VbnHf9hIRL ZpwUDJlw3YEBYXF0GpakjF9ghBiBG4HCdj/jOOVHf41UhF6yfaFtHBqFiP5mEbryLgy9 JlbA== X-Gm-Message-State: AOAM5337pSaHsGIfqvY84hxrGBg+kA2RTlUZAMS/gOh7HBlWc+LIbUKn SSn9QEcJRcS2eQHdMGCBiFsNTTGlXOkx/yNE X-Google-Smtp-Source: ABdhPJzxW58GoVDg9DXe3VlIIu6Zz+FBlV301B0hIass2XkT/B7p+K717pXSiFgUHOf4CH1xC9QxDtyYCzLn2SR8 X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:7220:84ff:fe09:7e9d]) (user=andreyknvl job=sendgmr) by 2002:a05:6214:1110:: with SMTP id e16mr16696575qvs.62.1612208638752; Mon, 01 Feb 2021 11:43:58 -0800 (PST) Date: Mon, 1 Feb 2021 20:43:32 +0100 In-Reply-To: Message-Id: <431c6cfa0ac8fb2b33d7ab561a64aa84c844d1a0.1612208222.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH 08/12] kasan, mm: optimize krealloc poisoning From: Andrey Konovalov To: 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-20210201_144402_891781_7C77D0AD X-CRM114-Status: GOOD ( 20.51 ) 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 , Andrew Morton , 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 9c64a00bbf9c..a51d6ea580b0 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..821f657d38b5 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 = __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; }