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Fri, 13 Oct 2023 13:54:12 -0700 (PDT) Date: Fri, 13 Oct 2023 13:54:08 -0700 From: Vishal Moola To: Hyesoo Yu Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: page_alloc: check the order of compound page event when the order is 0 Message-ID: References: <20231012011106.2425309-1-hyesoo.yu@samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231012011106.2425309-1-hyesoo.yu@samsung.com> X-Rspamd-Queue-Id: CC48AA001B X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: mjpdib1f1uxshhw59jtt75q5d31b9556 X-HE-Tag: 1697230453-285795 X-HE-Meta: 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 YJqsxY0o 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.421497, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 12, 2023 at 10:11:06AM +0900, Hyesoo Yu wrote: > For compound pages, the head sets the PG_head flag and > the tail sets the compound_head to indicate the head page. > If a user allocates a compound page and frees it with a different > order, the compound page information will not be properly > initialized. To detect this problem, compound_page(page) and > the order are compared, but it is not checked when the order is 0. > That error should be checked regardless of the order. I believe all compound pages are order >= 1, so this error can't occur when the order is 0.