From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jan Kara <jack@suse.cz>
Cc: Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
Subject: Re: [patch] ext4: underflow in alignment check
Date: Mon, 20 Jun 2016 19:53:26 +0000 [thread overview]
Message-ID: <20160620195325.GM32247@mwanda> (raw)
In-Reply-To: <20160620160204.GG6882@quack2.suse.cz>
On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> 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 <dan.carpenter@oracle.com>
>
> How come? (1 << 30) fits even into 32-bit signed type. So where's the
> problem?
Bad changelog... I was talking about a different issue. I was casting
it to unsigned to take advantage of type promototion. Assume we have:
int arg = 1 << 31;
(arg > (1 << 30)) // <-- this is false
(arg > (1U << 30)) // <-- this is true so there is no underflow.
regards,
dan carpenter
WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jan Kara <jack@suse.cz>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
Subject: Re: [patch] ext4: underflow in alignment check
Date: Mon, 20 Jun 2016 22:53:26 +0300 [thread overview]
Message-ID: <20160620195325.GM32247@mwanda> (raw)
In-Reply-To: <20160620160204.GG6882@quack2.suse.cz>
On Mon, Jun 20, 2016 at 06:02:04PM +0200, Jan Kara wrote:
> 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 <dan.carpenter@oracle.com>
>
> How come? (1 << 30) fits even into 32-bit signed type. So where's the
> problem?
Bad changelog... I was talking about a different issue. I was casting
it to unsigned to take advantage of type promototion. Assume we have:
int arg = 1 << 31;
(arg > (1 << 30)) // <-- this is false
(arg > (1U << 30)) // <-- this is true so there is no underflow.
regards,
dan carpenter
next prev parent reply other threads:[~2016-06-20 19:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 7:07 [patch] ext4: underflow in alignment check Dan Carpenter
2016-06-16 7:07 ` Dan Carpenter
2016-06-20 16:02 ` Jan Kara
2016-06-20 16:02 ` Jan Kara
2016-06-20 19:53 ` Dan Carpenter [this message]
2016-06-20 19:53 ` Dan Carpenter
2016-06-21 7:43 ` Jan Kara
2016-06-21 7:43 ` Jan Kara
2016-06-21 13:06 ` Dan Carpenter
2016-06-21 13:06 ` Dan Carpenter
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