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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1treSR-00000005BLY-3wxj; Mon, 10 Mar 2025 14:50:20 +0000 Date: Mon, 10 Mar 2025 14:50:19 +0000 From: Matthew Wilcox To: Vlastimil Babka Cc: Andrew Morton , netdev@vger.kernel.org, linux-mm@kvack.org, Hannes Reinecke Subject: Re: [PATCH] mm: Decline to manipulate the refcount on a slab page Message-ID: References: <20250310143544.1216127-1-willy@infradead.org> <598912d1-0482-434c-b7bb-75e6fdc2e38e@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <598912d1-0482-434c-b7bb-75e6fdc2e38e@suse.cz> X-Rspamd-Queue-Id: A290AA001B X-Stat-Signature: 1yj5da19dnsxtnth5r3wo53gxx7hbaib X-Rspamd-Server: rspam02 X-Rspam-User: X-HE-Tag: 1741618227-296422 X-HE-Meta: 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 lr2hwCfk 3DBZEFKxrDTFsoFhb/nTvDCc1CEAaENHzjbXkjc3moqVH3379J0BxKMl38uc4HS0YMVVuUmevCYrCGYGBqWGJLUL01H7e4NDucVE/CPAbCW64nUL7piSoZ9Y9L8wf93ImRBxfT3J6roLQ3LgXhscWQGV6eHNKOEU1rpHfZEiRXEEVYf7T3uaFEpRgdDfzGvqW/WPNKmEGaupB610bzQf8e4zBIyvkVc4z8pQB 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 Mon, Mar 10, 2025 at 03:37:51PM +0100, Vlastimil Babka wrote: > Note it's a 6.14 hotfix for kernel oopses due to page refcount overflow. Not actually overflow ... without VM_DEBUG enabled, networking increases the refcount from 0 to 1, then decrements it from 1 to 0, causing the slab to be freed. So it's a UAF bug induced by a messed-up refcount.