From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 65F6A2BAEB; Tue, 17 Sep 2024 12:36:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726576565; cv=none; b=AdyRnBcYWja898fRjLRa49JIz9ABdAlE1aLbdsZDYcWuy+ApwyC8zQ/ejHE5IAyqZ6PAbiOmbXK6/L5WSAJcbKCBkmV78aDaDAef3VG1Szp9Yke4YHRbtLuTnAWQatAPZV2ieri9etS7itaBixHIZGxfqbN6rwr1RqcNcRZ4ZCc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726576565; c=relaxed/simple; bh=xZEdMZsIYhBlrL7+PAFPW+dXzMkzNkdmM+dkkt+2NO0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=B+0TksnrG+fvavt1PBtKgXPnvlb60jA27l/bKIqQ+B+/QRHYqA2RZqOfhEqMAtTmS4XooGgfelfg0Emcmeq04s1JF0Xtlf+rV3XlFUEw3xgjgqEOoFt+6rA1dbf7TeAxEdP1j9iUtDH7EVR4zal/bEiu6TEJ2lKBAxJd9doX86c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz; spf=pass smtp.mailfrom=suse.cz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=DqdJ6zgz; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=52RkqkDz; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b=DqdJ6zgz; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b=52RkqkDz; arc=none smtp.client-ip=195.135.223.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=suse.cz Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.cz Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="DqdJ6zgz"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="52RkqkDz"; dkim=pass (1024-bit key) header.d=suse.cz header.i=@suse.cz header.b="DqdJ6zgz"; dkim=permerror (0-bit key) header.d=suse.cz header.i=@suse.cz header.b="52RkqkDz" Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 2FE042005A; Tue, 17 Sep 2024 12:36:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1726576561; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k0lB4qgIiJTwsTorinJVnENANKo2juI/k0mXnfHkVXw=; b=DqdJ6zgzBEiNvtQIj+SCX7w1StZs6Dp2UVcQ40vyykU42N4bNOsrb7prO0r6HyzCnNUvMf 6uIrkWvEaywqXv5GuKq9X3RIR1eHEc2cM4fciNsWp17W5a/WNEqamM72qu/fJvg8WPYBa/ S6m/OSd6zEHSXkbFmOOvnMQIUReqb7c= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1726576561; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k0lB4qgIiJTwsTorinJVnENANKo2juI/k0mXnfHkVXw=; b=52RkqkDzb8DyK5X6OBPUVuSmWgOO4vNZFDVNhiKsj3QPdmyjtf9FjO9EkJV7efLceTEy0i D4rLa/TqxS//2RCg== Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=DqdJ6zgz; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=52RkqkDz DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1726576561; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k0lB4qgIiJTwsTorinJVnENANKo2juI/k0mXnfHkVXw=; b=DqdJ6zgzBEiNvtQIj+SCX7w1StZs6Dp2UVcQ40vyykU42N4bNOsrb7prO0r6HyzCnNUvMf 6uIrkWvEaywqXv5GuKq9X3RIR1eHEc2cM4fciNsWp17W5a/WNEqamM72qu/fJvg8WPYBa/ S6m/OSd6zEHSXkbFmOOvnMQIUReqb7c= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1726576561; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=k0lB4qgIiJTwsTorinJVnENANKo2juI/k0mXnfHkVXw=; b=52RkqkDzb8DyK5X6OBPUVuSmWgOO4vNZFDVNhiKsj3QPdmyjtf9FjO9EkJV7efLceTEy0i D4rLa/TqxS//2RCg== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 1917613AB6; Tue, 17 Sep 2024 12:36:01 +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 3uYXBrF36WZcHwAAD6G6ig (envelope-from ); Tue, 17 Sep 2024 12:36:01 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 17BB9A086F; Tue, 17 Sep 2024 14:35:45 +0200 (CEST) Date: Tue, 17 Sep 2024 14:35:45 +0200 From: Jan Kara To: Fanqi Yu Cc: tytso@mit.edu, adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ext4: Prevent successful remount as r/w after filesystem abort Message-ID: <20240917123545.hmyj2ho4whpn2u67@quack3> References: <20240915210802.3835698-1-fanqi.yu@columbia.edu> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240915210802.3835698-1-fanqi.yu@columbia.edu> X-Rspamd-Queue-Id: 2FE042005A X-Spam-Level: X-Spamd-Result: default: False [-4.01 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_RHS_NOT_FQDN(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RCVD_COUNT_THREE(0.00)[3]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MIME_TRACE(0.00)[0:+]; ARC_NA(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; TO_DN_SOME(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCVD_TLS_LAST(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DNSWL_BLOCKED(0.00)[2a07:de40:b281:104:10:150:64:97:from,2a07:de40:b281:106:10:150:64:167:received]; FROM_EQ_ENVFROM(0.00)[]; RCPT_COUNT_FIVE(0.00)[5]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DKIM_TRACE(0.00)[suse.cz:+]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action X-Spam-Score: -4.01 X-Spam-Flag: NO On Sun 15-09-24 17:08:04, Fanqi Yu wrote: > While the order of writing to the shutdown and read-only flags has been > enforced by a write memory barrier, the read side in remount does not > have a pairing read barrier. > > In the event of a fs forced shutdown remounting as read-only, > remounting it again as read-write can succeed when the flag reads are > reordered such that sb_rdonly() returns true and > ext4_forced_shutdown() returns false. > > Commit 4418e14112e3 ("ext4: Fix fsync error handling after filesystem > abort") has added the other barriers related to these two flags but > seems to have missed this one. > > Signed-off-by: Fanqi Yu Thanks for the patch but there's a changed queued in ext4 tree [1] which removes setting of SB_RDONLY flag in emergency remount because it has other problems as well. And after this change the memory ordering problem you speak about is not an issue anymore. Honza [1] https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?h=dev&id=d3476f3dad4ad68ae5f6b008ea6591d1520da5d8 > --- > fs/ext4/super.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 044135796f2b..c5d3f8969dec 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -6542,6 +6542,13 @@ static int __ext4_remount(struct fs_context *fc, struct super_block *sb) > flush_work(&sbi->s_sb_upd_work); > > if ((bool)(fc->sb_flags & SB_RDONLY) != sb_rdonly(sb)) { > + > + /* > + * Make sure we read the updated s_ext4_flags. > + * Pairs with smp_wmb() in ext4_handle_error(). > + */ > + smp_rmb(); > + > if (ext4_forced_shutdown(sb)) { > err = -EROFS; > goto restore_opts; > -- > 2.34.1 > > -- Jan Kara SUSE Labs, CR