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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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260513095609.789935-1-lihongfu@kylinos.cn> X-Stat-Signature: zz5kad8yux6ix68e5a9ftd14x7mpo63i X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B513914000B X-Rspam-User: X-HE-Tag: 1778669886-776731 X-HE-Meta: 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 hnscTYGz dSjtWsUAEdSybq3ZLk3zM13AOSPPqcjPamUhbINhPJAJrzGLT7R9ozBUFJmOrlnVnt9zx83VszOYl6XaMs2Y40Rwl8OyvH0wS3K2cNxjtCvVrAn/rt4hqiMsyj5bRGzPNBK1aJx4MaZASg4wxUJ4f7QLCKQWw2q/KoHdmAq1YqSUqDCFQpDua3bqxGE4CwGRfubyqnkqJwAtcWY56Jn3jvwT00498h7JCxfGvrRANxJne5Hq83pQxuJ8Wv7lwzV99w/svfUqBlihQx4NMuTSmHUdsgsL6iD8u2oVjl+6sBcgLZ+LxzuopFJCY6lY9hn9eM5vUpOTv3qbgNd02QokvhJ3L3tgNavg/+mC4oxXrBl3VPhE= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 >