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 C5EB63AEB40; Wed, 13 May 2026 10:58:05 +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=1778669885; cv=none; b=p2JG8M8k0eD99AwWGn8+o4gDFsC72DnipFSSI5GtEgQAJQutPRTuwpF75S39DmJLsoIG+3qFJNY2/RRxtE465JNWb1u08taztDHRUBOwqC0vGL5gPXvndhMu1OTCeYjNrzZdEaLmOi+gPQKODtaPxgg2JZKJPjQ1EMl3tGbAoOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778669885; c=relaxed/simple; bh=8dhOi+LcaAZswGzRl4JIrjmJt8FqOC6s0xrrgcCEoI4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=osDR4NapTCqzrTxyLG3JLXaoFcdW2WzBp8cNF9L6VD8PTA0ywx3QqUfmrA5vEfxk0wcfWUvpdlpU40vLNqa+GpirvQhd4QfXsZktBgMXIVMorHI3fBtnLE9qNrdpamFei35Ruyp+bypmvLdxYg/snwCO6a7IJAboGZplrFcKrzo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=QIschZxi; 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="QIschZxi" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 783EEC2BCC7; Wed, 13 May 2026 10:58:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778669885; bh=8dhOi+LcaAZswGzRl4JIrjmJt8FqOC6s0xrrgcCEoI4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QIschZxiNsmY8s0D03sHvQp9kqpVbF1FRYyVa/C7nS2E0/uCwWfbBDvO+sCnilM5k /K3wBIuosK1gk9aviKsftT+26UqXjZyf3voiAAR4Ld1606I2fwyoVZyNZBU4nO+gmx qNRFhh5qkmteIhtO0lMdR9Ts2GktfnxDWtWZHM6n6LaRmg5oXlS0EvFZKEPSFbQXCU fDItq2cZJjr7vabuQcAEVpjxb8CsWipZLPlu1913MCiaG6Uj31rNpHtaUFw2AuN7P8 3KtEOtnV0Ih/0abPYHTW+Jq5gUwg1kDD1IbYJ9NhSSzVLo7hMyzkkZohvT8thj6evq sO8kPAISOzhHQ== Date: Wed, 13 May 2026 11:57:59 +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, Dev Jain Subject: Re: [PATCH v2] selftests/mm: Fix incorrect mmap() error handling with NULL instead of MAP_FAILED Message-ID: References: <20260513095609.789935-1-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: <20260513095609.789935-1-lihongfu@kylinos.cn> On Wed, May 13, 2026 at 05:56:09PM +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 > Reviewed-by: Dev Jain You forgot my tag :) Also, please do not send a respin right away if you can, multiple revisions in one day can be tricky to deal with. As per David's points - please update the commit message to reflect the fact you've added a missing assert too and replace the (void *)-1 with MAP_FAILED. Cheers, Lorenzo > --- > v2: > - Add missing mmap() return value checks in pkey_sighandler_tests.c > and protection_keys.c > --- > tools/testing/selftests/mm/ksm_tests.c | 2 +- > tools/testing/selftests/mm/madv_populate.c | 2 +- > tools/testing/selftests/mm/pkey_sighandler_tests.c | 2 ++ > tools/testing/selftests/mm/protection_keys.c | 1 + > tools/testing/selftests/mm/soft-dirty.c | 4 ++-- > tools/testing/selftests/mm/vm_util.c | 2 +- > 6 files changed, 8 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/pkey_sighandler_tests.c b/tools/testing/selftests/mm/pkey_sighandler_tests.c > index 302fef54049c..4637809192f9 100644 > --- a/tools/testing/selftests/mm/pkey_sighandler_tests.c > +++ b/tools/testing/selftests/mm/pkey_sighandler_tests.c > @@ -317,6 +317,7 @@ static void test_sigsegv_handler_with_different_pkey_for_stack(void) > /* Set up alternate signal stack that will use the default MPK */ > sigstack.ss_sp = mmap(0, STACK_SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > + assert(sigstack.ss_sp != MAP_FAILED); > sigstack.ss_flags = 0; > sigstack.ss_size = STACK_SIZE; > > @@ -490,6 +491,7 @@ static void test_pkru_sigreturn(void) > /* Set up alternate signal stack that will use the default MPK */ > sigstack.ss_sp = mmap(0, STACK_SIZE, PROT_READ | PROT_WRITE, > MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); > + assert(sigstack.ss_sp != MAP_FAILED); > sigstack.ss_flags = 0; > sigstack.ss_size = STACK_SIZE; > > diff --git a/tools/testing/selftests/mm/protection_keys.c b/tools/testing/selftests/mm/protection_keys.c > index 2085982dba69..580bf1668c71 100644 > --- a/tools/testing/selftests/mm/protection_keys.c > +++ b/tools/testing/selftests/mm/protection_keys.c > @@ -1217,6 +1217,7 @@ static void arch_force_pkey_reg_init(void) > * doing the XSAVE size enumeration dance. > */ > buf = mmap(NULL, 1*MB, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0); > + pkey_assert(buf != (void *)-1); Should use MAP_FAILED here as David pointed out. > > /* These __builtins require compiling with -mxsave */ > > 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 >