From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0D803E5A01; Wed, 13 May 2026 09:25:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778664339; cv=none; b=cJ5vPqHaozloEsmYEhd6Sr7Z7UnUS5lbYjrub1BMKWOljmGLvxoFD+UXpOjGbZ9WuXJ9UhyU+V6q+eh6cMpg5KqCnhg/f3GNLsS5VU0s2Q6mjwtOcgFt2Tf+lsruYEhPYrhRAUI8it3PUvU8CbOwzGM2WqHrKlig7jg4j3UnExE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778664339; c=relaxed/simple; bh=arxih0bDE+7RIMMJ1ElB/+tYtHu5uDaWxFo/FiWSgHk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bHrZJtzmwDzhpX5N/QnwpMUM7yokU7C0v4BBzPmN5byG06M7U2/yDRZwfI9su3zmS/8Gg0WW5n8uY9Y40fZgwiQGYFjuR7JzjPNDi+qfiqGSC1bKEpjN9MNVrWIkcB2tSZBc1mkUNPY7peK2BWevF0aq3XHgJZVpEMf8qxNIKqI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JNJ/sVju; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="JNJ/sVju" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 821C8C2BCB7; Wed, 13 May 2026 09:25:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778664339; bh=arxih0bDE+7RIMMJ1ElB/+tYtHu5uDaWxFo/FiWSgHk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JNJ/sVjuY+qBCCj/spXjuhopa6eqywKyu91VKIYkBVaVEbXB0E2HA598AiElBV4YD oFRs3Rryan4aVKqjlH5n++sbj3zU6gsXt34Ut2w74aidSogOdD0LUJ1vbLGst43asT P9rWPcdnNAcX5osE9S5TVIaPMc0kswwxyJuUx50of4g0syRYg86iMqnzKfZykQbCPS ZbZ5dfUCcTUHld0K0olZP+M0aOEQs8rmKnM9016+8JopRbY3oIYF7Khu1uC5XCs9dd 3jj3g21JuodgpVNF+AyhavzVaDVFXaajclFt0y4Ra1j2PfjOfr+zgmSJ/1sJHPRQME AshkCw2gcxbvA== Date: Wed, 13 May 2026 10:25:33 +0100 From: Lorenzo Stoakes To: Hongfu Li Cc: akpm@linux-foundation.org, david@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] selftests/mm: Fix incorrect mmap() error handling with NULL instead of MAP_FAILED Message-ID: References: <20260513025223.592766-1-lihongfu@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260513025223.592766-1-lihongfu@kylinos.cn> On Wed, May 13, 2026 at 10:52:23AM +0800, 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 Ugh how did we end up with all of these :) thanks for the fix, assuming you get all of the other cases on respin, feel free to attach my tag to that: Reviewed-by: Lorenzo Stoakes Cheers, Lorenzo > --- > 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"); > -- > 2.25.1 >