From: tytso@mit.edu Subject: Re: [PATCH V2] ext4: handle optional-arg mount options better Date: Mon, 15 Feb 2010 20:19:44 -0500 Message-ID: <20100216011944.GQ5337@thunk.org> References: <4B69E6FA.20901@redhat.com> <20100215160150.GJ5337@thunk.org> <4B79BA90.3060703@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: ext4 development To: Eric Sandeen Return-path: Received: from thunk.org ([69.25.196.29]:51639 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932437Ab0BPBTq (ORCPT ); Mon, 15 Feb 2010 20:19:46 -0500 Content-Disposition: inline In-Reply-To: <4B79BA90.3060703@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Ok, how about this, for even more explicit? - Ted commit 15121c18a22ae483279f76dc9e554334b800d0f7 Author: Eric Sandeen Date: Mon Feb 15 20:17:55 2010 -0500 ext4: Fix optional-arg mount options We have 2 mount options, "barrier" and "auto_da_alloc" which may or may not take a 1/0 argument. This causes the ext4 superblock mount code to subtract uninitialized pointers and pass the result to kmalloc, which results in very noisy failures. Per Ted's suggestion, initialize the args struct so that we know whether match_token() found an argument for the option, and skip match_int() if not. Also, return error (0) from parse_options if we thought we found an argument, but match_int() Fails. Reported-by: Michael S. Tsirkin Signed-off-by: Eric Sandeen Signed-off-by: "Theodore Ts'o" diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 735c20d..68a55df 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1229,6 +1229,11 @@ static int parse_options(char *options, struct super_block *sb, if (!*p) continue; + /* + * Initialize args struct so we know whether arg was + * found; some options take optional arguments. + */ + args[0].to = args[0].from = 0; token = match_token(p, tokens, args); switch (token) { case Opt_bsd_df: @@ -1518,10 +1523,11 @@ set_qf_format: clear_opt(sbi->s_mount_opt, BARRIER); break; case Opt_barrier: - if (match_int(&args[0], &option)) { - set_opt(sbi->s_mount_opt, BARRIER); - break; - } + if (args[0].from) { + if (match_int(&args[0], &option)) + return 0; + } else + option = 1; /* No argument, default to 1 */ if (option) set_opt(sbi->s_mount_opt, BARRIER); else @@ -1594,10 +1600,11 @@ set_qf_format: set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC); break; case Opt_auto_da_alloc: - if (match_int(&args[0], &option)) { - clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC); - break; - } + if (args[0].from) { + if (match_int(&args[0], &option)) + return 0; + } else + option = 1; /* No argument, default to 1 */ if (option) clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC); else