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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=Eem+CPI6cqDr3+sdydeGQiL8gIW8yui8+/Xm+DAKB7k=; b=X5HnhTbTyYAGu/dRTbIniijFWx9gLZLqqZf6wJDzizrPgxU8jvEFsPgk6J2BuYTwdG 3+mBRkjEzWXCKb+qAnmfv0RkHYI+8+thkEgzWQ9w7EaDzG9oThGjWg3XcGywQ57oAtky jPYvqv2tFr5VHLWPvZK8/6ARGS/hGn4XMg8taWhP42zatkMpyRgxoC8datKkqFq58pzN EG5OxXFNMP1zPeq4wKIUzeyrWLJNqK7R5kaggngm/slaHlUX3RxRPTKpQDkbVRyBNaxg 6cHd6GvADDdaKVMqLX8HnU4nBwr7wpbJogbAjjBlWvQScP0GS3kwJB+N8DGXd4gtqCFQ PFgA== X-Gm-Message-State: AOAM530yUcaiwx4y3rxpgc0lBKVNuqBoK+gGSKoPUD3OoKsrHb+3DAmh DLKG1qYw9l/i+QJlkfV6MXJxywvstSOmoyJD X-Google-Smtp-Source: ABdhPJyqQdKHrhOuNMT3pVa3R7FPH70A7UVF1EhvgAytPKqWBBtNMrRHXWGCczaKH2RqOThi7wWAhXKWKxUeKXJY X-Received: from andreyknvl3.muc.corp.google.com ([2a00:79e0:15:13:edb8:b79c:2e20:e531]) (user=andreyknvl job=sendgmr) by 2002:a1c:25c2:: with SMTP id l185mr4086468wml.62.1612539574962; Fri, 05 Feb 2021 07:39:34 -0800 (PST) Date: Fri, 5 Feb 2021 16:39:08 +0100 In-Reply-To: Message-Id: <419e4e7ac9ff7596a1a0956c117fcad1938e5d77.1612538932.git.andreyknvl@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.30.0.365.g02bc693789-goog Subject: [PATCH v2 07/12] kasan, mm: fail krealloc on freed objects From: Andrey Konovalov To: Andrew Morton , Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Marco Elver Cc: Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev@googlegroups.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrey Konovalov 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: Currently, if krealloc() is called on a freed object with KASAN enabled, it allocates and returns a new object, but doesn't copy any memory from the old one as ksize() returns 0. This makes the caller believe that krealloc() succeeded (KASAN report is printed though). This patch adds an accessibility check into __do_krealloc(). If the check fails, krealloc() returns NULL. This check duplicates the one in ksize(); this is fixed in the following patch. This patch also adds a KASAN-KUnit test to check krealloc() behaviour when it's called on a freed object. Reviewed-by: Marco Elver Signed-off-by: Andrey Konovalov --- lib/test_kasan.c | 20 ++++++++++++++++++++ mm/slab_common.c | 3 +++ 2 files changed, 23 insertions(+) diff --git a/lib/test_kasan.c b/lib/test_kasan.c index 6e63ba62db09..791164ef191b 100644 --- a/lib/test_kasan.c +++ b/lib/test_kasan.c @@ -359,6 +359,25 @@ static void krealloc_pagealloc_less_oob(struct kunit *test) KMALLOC_MAX_CACHE_SIZE + 201); } +/* + * Check that krealloc() detects a use-after-free, returns NULL, + * and doesn't unpoison the freed object. + */ +static void krealloc_uaf(struct kunit *test) +{ + char *ptr1, *ptr2; + int size1 = 201; + int size2 = 235; + + ptr1 = kmalloc(size1, GFP_KERNEL); + KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr1); + kfree(ptr1); + + KUNIT_EXPECT_KASAN_FAIL(test, ptr2 = krealloc(ptr1, size2, GFP_KERNEL)); + KUNIT_ASSERT_PTR_EQ(test, (void *)ptr2, NULL); + KUNIT_EXPECT_KASAN_FAIL(test, *(volatile char *)ptr1); +} + static void kmalloc_oob_16(struct kunit *test) { struct { @@ -1056,6 +1075,7 @@ static struct kunit_case kasan_kunit_test_cases[] = { KUNIT_CASE(krealloc_less_oob), KUNIT_CASE(krealloc_pagealloc_more_oob), KUNIT_CASE(krealloc_pagealloc_less_oob), + KUNIT_CASE(krealloc_uaf), KUNIT_CASE(kmalloc_oob_16), KUNIT_CASE(kmalloc_uaf_16), KUNIT_CASE(kmalloc_oob_in_memset), diff --git a/mm/slab_common.c b/mm/slab_common.c index 39d1a8ff9bb8..dad70239b54c 100644 --- a/mm/slab_common.c +++ b/mm/slab_common.c @@ -1140,6 +1140,9 @@ 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); if (ks >= new_size) {