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Mon, 08 Dec 2025 12:13:40 -0800 (PST) Received: from dkarn-thinkpadp16vgen1.punetw6.csb ([2402:e280:3e0d:a45:3861:8b7f:6ae1:6229]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29daeaabf5fsm133395645ad.78.2025.12.08.12.13.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 08 Dec 2025 12:13:40 -0800 (PST) From: Deepakkumar Karn To: djwong@kernel.org Cc: brauner@kernel.org, dkarn@redhat.com, jack@suse.cz, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+e07658f51ca22ab65b4e@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Subject: Re: [PATCH v2] fs: add NULL check in drop_buffers() to prevent null-ptr-deref Date: Tue, 9 Dec 2025 01:43:33 +0530 Message-ID: <20251208201333.528909-1-dkarn@redhat.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251208193024.GA89444@frogsfrogsfrogs> References: <20251208193024.GA89444@frogsfrogsfrogs> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Mon, 8 Dec 2025 11:30:24 -0800, Darrick J. Wong wrote: > > drop_buffers() dereferences the buffer_head pointer returned by > > folio_buffers() without checking for NULL. This leads to a null pointer > > dereference when called from try_to_free_buffers() on a folio with no > > buffers attached. This happens when filemap_release_folio() is called on > > a folio belonging to a mapping with AS_RELEASE_ALWAYS set but without > > release_folio address_space operation defined. In such case, > What user is that? All the users of AS_RELEASE_ALWAYS in 6.18 appear to > supply a ->release_folio. Is this some new thing in 6.19? AFS directories SET AS_RELEASE_ALWAYS but have not .release_folio.