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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3687868ac48sm1338887f8f.29.2024.07.19.04.19.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jul 2024 04:19:29 -0700 (PDT) Date: Fri, 19 Jul 2024 13:19:29 +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: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 1e1omamwwtfoekquf14icmp54jhr61cb X-Rspam-User: X-Rspamd-Queue-Id: B530EC0028 X-Rspamd-Server: rspam02 X-HE-Tag: 1721387971-648453 X-HE-Meta: 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 GcHSbZ6r Q9j7xIvtiXKA2rrblV8CWCAdi0Dmmh2LASb3tDQnYeQ6hY8ENSekyue80bA0Uzbq16LRXIzhFp7yCudPd3LMEuXEWbfxRrXG5XoIOS8G6rSQO1dUD3b8UGl3U3znSgLHd4mtxC5hL4PlBp/igfXgOpecozq3+dfaoXhPWA+4u7NrA8cpH87QMDi0wROBx9vHQ3g9HQKlgb9T9C3pHXOrqEu5NnVqcv5CxntMcN85BWAxb3RMPj4LtC4aL2rqKGXntQfd1DDqgKR7NeKFCU0jE6mSyN0LRgeuCKnXCYmcEmsR5AfrPTIOh6l3Pi3yzaQtZwz9qmJDGdZMSn/OLoyfFmlhGMBNE1Sm9aog12Kozaq8rgDU65yo0/IIvZir+U29MkbAwIkSb6Pl3KmiZ5szrbYcjZg== 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 Fri 19-07-24 23:05:48, Barry Song wrote: [...] > BTW, we are really exposing potential exploits. Rather than an early > stage BUG_ON(), is it reasonable to BUG_ON when we really return > NULL for NOFAIL at the last moment? This will crash the system but it > is still safer than exposing exploits. I believe the whole discssion here revolves around either using BUG_ON or retrying without any sleep. But I guess you are specifically talking about those two original k[v]malloc_array* interfaces which have introduced the early break. For those BUG_ON is a safer option than WARN_ON definitely. Please involve Kees who has introduced those. kvmalloc_node_noprof would require something similar. It checks for INT_MAX. You can test whether Linus is OK with such a change that way ;) Good luck -- Michal Hocko SUSE Labs