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From: Kent Overstreet To: Youling Tang Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Youling Tang Subject: Re: [PATCH] mm: list_lru: Fix NULL pointer dereference in list_lru_add() Message-ID: References: <20240712032554.444823-1-youling.tang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240712032554.444823-1-youling.tang@linux.dev> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: B2530140011 X-Stat-Signature: h1zgtmftr9jwzgbwkiqr3fwbhar6zsb7 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1720757272-853293 X-HE-Meta: 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 4eIONWA6 /2N15V/DT2MK80apM9yqfTVVPN5SUtpiZJXBWYAYoXV8zePb+uW8GUJPBDKuojUHEDho5PhRgfth/yh4DC8pzzmx6eFHVRYxiNMRBWIO/3STETsFiRUO7EJ3Qm4pb2qGsckas9O5ADnDbZNsXcpSWQ0Bdlc0fkalsml3dV6zHYyhgy4wCZF97hj2iDhqEeNJHDbKRtBOWKGclCRDX0QUoRRL5nxGp49lS/qnSw3yJbxmBaeLHpmsguKaKUQ== 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, Jul 12, 2024 at 11:25:54AM GMT, Youling Tang wrote: > From: Youling Tang > > Note that list_lru_from_memcg_idx() may return NULL, so it is necessary > to error handle the return value to avoid triggering NULL pointer > dereference BUG. > > The issue was triggered for discussion [1], > Link [1]: https://lore.kernel.org/linux-bcachefs/84de6cb1-57bd-42f7-8029-4203820ef0b4@linux.dev/T/#m901bb26cdb1d9d4bacebf0d034f0a5a712cc93a6 I see no explanation for why this is the correct fix, and I doubt it is. What's the real reason for the NULL lru_list_one, and why doesn't this come up on other filesystems?