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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 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 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B035FA0003 X-Stat-Signature: 7d4y7id15dn5ku7ir85osrhwzgu48yw1 X-Rspam-User: X-HE-Tag: 1778646462-619789 X-HE-Meta: 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 +yGGwbrp m2X0/EDc+0SidtVBggCKRT6wnzdN29iCO3qCs8LuYwjcKhxN0IemAVR2cONxEZz96y/Yy3yBZqJWOjk9h6hDlYt19QX/B5FtddIvNRW8ouLGOkYJwfYamGQbhMq9G59omobRIsvCuKHiDTAxJX6GGvT0oGMPZYWIw8pjiQiGAELgbwpFtHrN9lodPMNlu7i/a0jnw6SV9/MOOafQvalKTFsUG48ZOZBtUw4W3FZmeuyRWuZNL6TlnXrwknq9+ETOolp9HXaTfvgRd82fw9f0XMcHwRiRmvK3uzpVjDWB/QA3/kbcHzPCxsfOb/99jeVTkFLrOYtq99FlmAFUxhHTAjiSiwQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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");