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Thu, 12 Mar 2026 23:22:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id IcsrO8ZKs2k6HQAAD6G6ig (envelope-from ); Thu, 12 Mar 2026 23:22:46 +0000 Date: Thu, 12 Mar 2026 23:22:45 +0000 From: Pedro Falcato To: Andrew Morton Cc: Josh Law , "Liam R . Howlett" , Alice Ryhl , Andrew Ballance , Josh Law , maple-tree@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] lib/maple_tree: fix potential NULL dereference in mas_pop_node() Message-ID: References: <20260312184054.23481-1-objecting@objecting.org> <20260312134531.49c1f9171b4b0bc8352e678d@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260312134531.49c1f9171b4b0bc8352e678d@linux-foundation.org> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 5E75E4000A X-Stat-Signature: kzfcmxianootxi7r13uwgnb8cz9p4gj6 X-Rspam-User: X-HE-Tag: 1773357769-373735 X-HE-Meta: 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 fWnCacBW 4l4uXc+kt6kO8EM2t/o45fDm/5g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Mar 12, 2026 at 01:45:31PM -0700, Andrew Morton wrote: > On Thu, 12 Mar 2026 18:40:53 +0000 Josh Law wrote: > > > If kmem_cache_alloc_from_sheaf() returns NULL (possible under > > GFP_NOWAIT pressure), mas_pop_node() falls through to the out label > > and dereferences the NULL pointer in memset(ret, 0, sizeof(*ret)). > > This is such a glaring bug that I wonder if we're missing something. According to my local copy of lib/maple_tree.c: mas_pop_node() - Get a previously allocated maple node from the maple state. Note the "previously" :) kmem_cache_alloc_from_sheaf() can only fail if you run out of objects in the sheaf. So yeah, this "bug" looks bogus. -- Pedro