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b=n1SaE/UXjiCHBf1j7Ibstsr+IIFW0TAzyTpHFI5N3CeDYI3tgiRahva+tQ+zVQ/Pw x/fgsWMlh5odItFO3eG8EEghC/O1j8YnY8mu2yW55/D50ygWJt20BUkqTxFVVYO1v0 6HB6n/ojktO0vJvXiYX2WlEXw7m3g5EkKxea6H7w= Date: Wed, 7 May 2025 15:33:25 -0700 From: Andrew Morton To: Jeongjun Park Cc: urezki@gmail.com, edumazet@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/vmalloc: fix data race in show_numa_info() Message-Id: <20250507153325.48726051dbbff4f3936a83ff@linux-foundation.org> In-Reply-To: <20250507142552.9446-1-aha310510@gmail.com> References: <20250507142552.9446-1-aha310510@gmail.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: CFAD314000A X-Stat-Signature: j4rz7md4x8o8eyotf9qoy91p9asfxjt7 X-Rspam-User: X-HE-Tag: 1746657207-50813 X-HE-Meta: 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 P47r3yWJ EQihbcatdocjYySooiXsoNdm7eNRFpoqf8P+lwSP0EibNf+AZPGHwkLAwoZdg7CTHetiHaVC1mDPUJGJRt1RjT4JtFeLRE/jBjRQGGSKwfTpYW4nvFVlfjH0h4dRh1R5XbJGNlJEJ6lPzvPp0KeeNBcHt0wfs+lmivZgL/CBeLu+EXol1UZCS9Gi1wSepBvVw1ifbc5Y+1CZrrLw0ZZ7/q/E71427CLiGKIn5fJUCizlprHQah3012+m8vNBZmQp1mbZW5evgjG1/Ee0+L1EtMzwC/Yqvbn5Z/SvBlFcjO4QKc+Z7uuwLyDeIc6EUBQ4sEgfv 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 Wed, 7 May 2025 23:25:52 +0900 Jeongjun Park wrote: > The following data-race was found in show_numa_info(): > > ... > > > According to this report, there is a read/write data-race because m->private > is accessible to multiple CPUs. To fix this, instead of allocating the heap > in proc_vmalloc_init() and passing the heap address to m->private, > show_numa_info() should allocate the heap. > > One thing to note is that show_numa_info() is called in a critical section > of a spinlock, so it must be allocated on the heap with GFP_ATOMIC flag. GFP_ATOMIC is unfortunate. Can vmalloc_info_show() allocate the storage outside the lock and pass that pointer into show_numa_info()? That way will be more efficient also, less allocating and freeing.