From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Date: Mon, 20 Jun 2016 16:02:04 +0000 Subject: Re: [patch] ext4: underflow in alignment check Message-Id: <20160620160204.GG6882@quack2.suse.cz> List-Id: References: <20160616070709.GC23129@mwanda> In-Reply-To: <20160616070709.GC23129@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Dan Carpenter Cc: Theodore Ts'o , Andreas Dilger , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org On Thu 16-06-16 10:07:09, Dan Carpenter wrote: > My static checker complains that this can underflow if arg is negative > which is true. > > Signed-off-by: Dan Carpenter How come? (1 << 30) fits even into 32-bit signed type. So where's the problem? Honza > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index b1a3471..a2a17e9 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -1576,7 +1576,7 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token, > } else if (token = Opt_min_batch_time) { > sbi->s_min_batch_time = arg; > } else if (token = Opt_inode_readahead_blks) { > - if (arg && (arg > (1 << 30) || !is_power_of_2(arg))) { > + if (arg && (arg > (1U << 30) || !is_power_of_2(arg))) { > ext4_msg(sb, KERN_ERR, > "EXT4-fs: inode_readahead_blks must be " > "0 or a power of 2 smaller than 2^31"); > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Jan Kara SUSE Labs, CR