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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a79bc5b73ddsm524162566b.58.2024.07.18.00.27.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Jul 2024 00:27:41 -0700 (PDT) Date: Thu, 18 Jul 2024 09:27:40 +0200 From: Michal Hocko To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, linux-mm@kvack.org, Barry Song , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL Message-ID: References: <20240717230025.77361-1-21cnbao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 58028100011 X-Stat-Signature: 7bpmpx7fk7x8f6mzr5um7azxfk6phipx X-Rspam-User: X-HE-Tag: 1721287663-136133 X-HE-Meta: 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 fgBn35kR COyygSTdhqL9NSOAa/Mv9OZb+zYAitqZZcxZ2G550tI5P59j47aud8WpmBEeBp0zXHnVjHjLwt6q1Oa4n/DYLjrxxWzNIZzEpeL/8RtvAkqEt+elwwt4W2ZAthQP4m0BtEeAooOOR7xHIJK4JNaaf4BuBp9jlmNjc5G6oC+jC6EO3JWwMEj8x3ISlHKjFsJG2uMsMZwoOB9RwrLWOeDegymUIUB7ONpH7BSyf8/6B8VsCTfH7Ql4QrerhvDXjRzDmw5O9OYosdXH/HVZvvKvFjyorxFjMP7PG8Z4p/x8NrXHv+l7dEa/pPGYk+73Zu55Xp+V0Noc2/Ea+jvsKaPh9khL0EHAGR9xBSldkwIeDfssaEgDLj7LCwR9VJnyqKSyXU5tQ3Cc/79wmtU/lJEk64eqjRdS2lgzS4avNAaxOb6Ic7tc= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 18-07-24 19:22:37, Barry Song wrote: [...] > For future-proofing and security reasons, returning NULL for NOFAIL > still seems incorrect as the callers won't check the ret. If any future or > existing in-tree code has a potential bug which might be exploited by > hackers, for example > > ptr = kvmalloc_array(NOFAIL); > ptr->callback(); //ptr=NULL; > > callback could be a privilege escalation? Only if you allow to map zero page AFAIK. Nobody reasonable should be doing that. -- Michal Hocko SUSE Labs