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b=egQzb8mjFyNnn+lIWZTsTJk4rD/PWO+MJWaS96RqxXXY3WhdlXpL5XJE8DyXkm75C 6SGAhgCDmZxl6qVmCpsXrYnYY/z7JQ2CHa2ytHUJ4jP3/xmPY6ntSuAsKfi/EhoNvx /JavDPD/oBAoCq+smnpFtH/vMULVmp4kERvnftM8RI4aX/EE8fu8hs2nVp1Szg9H3T jcTAbdhviP+Qp6Okve8J1TZgEcWLI0rncY/SrPdmFroq/anunCsQAm2bGvlDCfNied yUTGqSW3LHRtF6/LvgPt1kv1hnFRxf8w95DxLZeOgblLj8oJwdkmGNuWlsl25too9a Do2yrfe7UpXoQ== Message-ID: <9e302879-d218-4257-9e2b-e468564b89ea@kernel.org> Date: Wed, 13 May 2026 12:05:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] selftests/mm: Fix incorrect mmap() error handling with NULL instead of MAP_FAILED To: Hongfu Li , akpm@linux-foundation.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, Dev Jain References: <20260513095609.789935-1-lihongfu@kylinos.cn> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 966F34000C X-Rspam-User: X-Stat-Signature: ekgpiawj4rfi1wox93dgbhr3zz4tib4j X-HE-Tag: 1778666755-749271 X-HE-Meta: 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 alorPT3j hQR1dcyyGuWLk5gXQCnSoXDPnvDYu91UwDdGfz9s9+htERB8em3LyDTvvV9AQgilQG/v7NgBAj+lVEWa9FuYrzkxPu/ro9467xrMiYJWWtf4N8/iYyY30f0Ys6CdxmNYSyPkp/sUistC92QwmqhO2Hkhi2qGt9FUbLtwgagpVrKeqR5N1ja/+jLniCyqAARsrUQLgAar8vmkvPxOnWss3r25JHaaOy8Yu6Jqk4yyx77zaRLudnszaQXCFLJWlLiqIvsPw48ig25Au1TxzU1YNwYpbHj3nBLJox7EEL6KQ9aztoxZRhdkW6gUOjbFzf3+s+Zn13BxYh2BvlsQvjKDV6bejyuQUKuydTvN73BH2Uh3yyqA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 5/13/26 11:56, 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. Well, your patch also adds more checks where we previously didn't have any checks? > > Signed-off-by: Hongfu Li > Reviewed-by: Dev Jain > --- > v2: > - Add missing mmap() return value checks in pkey_sighandler_tests.c > and protection_keys.c > --- [...] > 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); What's the reason for not using MAP_FAILED? -- Cheers, David