From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 896E01991D4; Wed, 13 May 2026 04:27:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778646465; cv=none; b=YKkCS74GQ39ugkHIivi1UOFYv/5kraG36LnXskBX973Q7f2zn/Zx92DD7QmZjo0OWiuwrJES9MOkx8I4KJmn9DdqCKWx8wxgoSyJCOB8CcFss000d9qeOXvatGU139bF2/m7hW+y/hIbub5nWSjSAd8chLBZOO016Kqtvtf2UBs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778646465; c=relaxed/simple; bh=exUFgKkNOkgX3YbRJeprGMKAC+3rhwrdVrR7Yx6ey4E=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=P2n1kCZIFKy/iR+qXasmxJOZ+vwlZNWNuaBTktJfHKXCpGeNU9fLxfiXymYLQI+DLsU0dwj4Zjyrnsvi0lMh7rgChm8QVTVD6kHAMYpfJzNPVvCss8FBapSY8amjsH+bJbGCJXvKaEhO7jpCtq/4K0EAj84aWFHpg5nSLTheXZ8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=MisppLS7; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="MisppLS7" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 34DD9175D; Tue, 12 May 2026 21:27:36 -0700 (PDT) Received: from [10.164.148.43] (MacBook-Pro.blr.arm.com [10.164.148.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 160763F7B4; Tue, 12 May 2026 21:27:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1778646461; bh=exUFgKkNOkgX3YbRJeprGMKAC+3rhwrdVrR7Yx6ey4E=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=MisppLS7KSQE6vaB5iWyhqRQsWvqws7p6GFbzW+ZqOvt/9JO13Z5DsRmJCDGP/aiH Jv6aCL2jgu+FrSxLuE/vDcGWk9c5VGW9ejelVN12ErUz3QCVGaoekVw2R2OvDIBC8U 0kdtyL6lQvRQ7ZlTXTJ/MME/jdUPvE7Y/kP8qHzA= Message-ID: <04203abd-b729-40cf-87e4-186b12c17298@arm.com> Date: Wed, 13 May 2026 09:57:27 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: Fix incorrect mmap() error handling with NULL instead of MAP_FAILED To: Hongfu Li , akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260513025223.592766-1-lihongfu@kylinos.cn> Content-Language: en-US From: Dev Jain In-Reply-To: <20260513025223.592766-1-lihongfu@kylinos.cn> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 13/05/26 8:22 am, Hongfu Li wrote: > mmap() returns MAP_FAILED, which is defined as (void *)-1, on error, > not NULL. Several selftests incorrectly check the return value of > mmap() using !ptr or ptr == NULL, which would erroneously treat > MAP_FAILED as a valid pointer since MAP_FAILED is non-zero and > non-NULL. This can lead to segfaults when mmap() actually fails > under memory pressure. > > Signed-off-by: Hongfu Li Hopefully you have fixed all instances in selftests/mm :) Reviewed-by: Dev Jain > --- > tools/testing/selftests/mm/ksm_tests.c | 2 +- > tools/testing/selftests/mm/madv_populate.c | 2 +- > tools/testing/selftests/mm/soft-dirty.c | 4 ++-- > tools/testing/selftests/mm/vm_util.c | 2 +- > 4 files changed, 5 insertions(+), 5 deletions(-) > > diff --git a/tools/testing/selftests/mm/ksm_tests.c b/tools/testing/selftests/mm/ksm_tests.c > index a0b48b839d54..ed481f817282 100644 > --- a/tools/testing/selftests/mm/ksm_tests.c > +++ b/tools/testing/selftests/mm/ksm_tests.c > @@ -174,7 +174,7 @@ static void *allocate_memory(void *ptr, int prot, int mapping, char data, size_ > { > void *map_ptr = mmap(ptr, map_size, PROT_WRITE, mapping, -1, 0); > > - if (!map_ptr) { > + if (map_ptr == MAP_FAILED) { > perror("mmap"); > return NULL; > } > diff --git a/tools/testing/selftests/mm/madv_populate.c b/tools/testing/selftests/mm/madv_populate.c > index 88050e0f829a..7fce5d0b622b 100644 > --- a/tools/testing/selftests/mm/madv_populate.c > +++ b/tools/testing/selftests/mm/madv_populate.c > @@ -34,7 +34,7 @@ static void sense_support(void) > > addr = mmap(0, pagesize, PROT_READ | PROT_WRITE, > MAP_ANONYMOUS | MAP_PRIVATE, 0, 0); > - if (!addr) > + if (addr == MAP_FAILED) > ksft_exit_fail_msg("mmap failed\n"); > > ret = madvise(addr, pagesize, MADV_POPULATE_READ); > diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c > index bcfcac99b436..67c26c265880 100644 > --- a/tools/testing/selftests/mm/soft-dirty.c > +++ b/tools/testing/selftests/mm/soft-dirty.c > @@ -143,7 +143,7 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon) > if (anon) { > map = mmap(NULL, pagesize, PROT_READ|PROT_WRITE, > MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); > - if (!map) > + if (map == MAP_FAILED) > ksft_exit_fail_msg("anon mmap failed\n"); > } else { > test_fd = open(fname, O_RDWR | O_CREAT, 0664); > @@ -155,7 +155,7 @@ static void test_mprotect(int pagemap_fd, int pagesize, bool anon) > ftruncate(test_fd, pagesize); > map = mmap(NULL, pagesize, PROT_READ|PROT_WRITE, > MAP_SHARED, test_fd, 0); > - if (!map) > + if (map == MAP_FAILED) > ksft_exit_fail_msg("file mmap failed\n"); > } > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index db94564f4431..63aaa2d9ec0b 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -463,7 +463,7 @@ bool softdirty_supported(void) > /* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */ > addr = mmap(0, pagesize, PROT_READ | PROT_WRITE, > MAP_ANONYMOUS | MAP_PRIVATE, 0, 0); > - if (!addr) > + if (addr == MAP_FAILED) > ksft_exit_fail_msg("mmap failed\n"); > > supported = check_vmflag(addr, "sd");