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Mon, 11 Mar 2024 10:34:50 +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 CtzgCEre7mU0HQAAD6G6ig (envelope-from ); Mon, 11 Mar 2024 10:34:50 +0000 Received: from localhost (brahms.olymp [local]) by brahms.olymp (OpenSMTPD) with ESMTPA id 521d665d; Mon, 11 Mar 2024 10:34:49 +0000 (UTC) From: Luis Henriques To: Miklos Szeredi Cc: "Theodore Ts'o" , Andreas Dilger , Alexander Viro , Christian Brauner , Jan Kara , Amir Goldstein , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] ovl: fix the parsing of empty string mount parameters In-Reply-To: (Miklos Szeredi's message of "Mon, 11 Mar 2024 10:25:20 +0100") References: <20240307160225.23841-1-lhenriques@suse.de> <20240307160225.23841-4-lhenriques@suse.de> Date: Mon, 11 Mar 2024 10:34:49 +0000 Message-ID: <87le6p6oqe.fsf@suse.de> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Level: Authentication-Results: smtp-out1.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=TE1SX6Jd; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=L81a4abe X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-1.56 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; RCVD_COUNT_THREE(0.00)[4]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; MX_GOOD(-0.01)[]; RCPT_COUNT_SEVEN(0.00)[11]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_CC(0.00)[mit.edu,dilger.ca,zeniv.linux.org.uk,kernel.org,suse.cz,gmail.com,vger.kernel.org]; MID_RHS_MATCH_FROM(0.00)[]; BAYES_HAM(-0.05)[60.05%] X-Spam-Score: -1.56 X-Rspamd-Queue-Id: E53AB34B28 X-Spam-Flag: NO Miklos Szeredi writes: > On Thu, 7 Mar 2024 at 19:17, Luis Henriques wrote: >> >> This patch fixes the usage of mount parameters that are defined as strin= gs >> but which can be empty. Currently, only 'lowerdir' parameter is in this >> situation for overlayfs. But since userspace can pass it in as 'flag' >> type (when it doesn't have a value), the parsing will fail because a >> 'string' type is assumed. > > I don't really get why allowing a flag value instead of an empty > string value is fixing anything. > > It just makes the API more liberal, but for what gain? The point is that userspace may be passing this parameter as a flag and not as a string. I came across this issue with ext4, by doing something as simple as: mount -t ext4 -o usrjquota=3D /dev/sda1 /mnt/ (actually, the trigger was fstest ext4/053) The above mount should succeed. But it fails because 'usrjquota' is set to a 'flag' type, not 'string'. Note that I couldn't find a way to reproduce the same issue in overlayfs with this 'lowerdir' parameter. But looking at the code the issue is similar. Cheers, --=20 Lu=C3=ADs