From: Dan Carpenter <dan.carpenter@oracle.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Joern Engel <joern@lazybastard.org>,
yangerkun <yangerkun@huawei.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-mtd@lists.infradead.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mtd: phram: Prevent divide by zero bug in phram_setup()
Date: Fri, 21 Jan 2022 14:51:03 +0300 [thread overview]
Message-ID: <20220121115103.GH1978@kadam> (raw)
In-Reply-To: <20220121121748.24e98015@xps13>
On Fri, Jan 21, 2022 at 12:17:48PM +0100, Miquel Raynal wrote:
> Hi Dan,
>
> dan.carpenter@oracle.com wrote on Fri, 21 Jan 2022 08:38:36 +0300:
>
> > The problem is that "erasesize" is a uint32_t type so it might be
>
> Don't you mean uint64_t here? Otherwise I don't get the sentence.
>
Yeah. I meant uint64_t. Will resend.
> > non-zero but the truncated "(uint32_t)erasesize" value *is* zero. That
>
> s/*is*/*can* be/ ? (again, if my understanding is correct).
>
It might be a situation where "erasesize" is non-zero but after we
truncated it "(uint32_t)erasesize" is zero.
> > would lead to the divide by zero bug.
> >
> > Avoid the bug by delaying the divide until after we have validated
> > that "erasesize" is reasonable.
>
> I don't really get the fix. If "erasesize" is big enough, then
> (uint32_t)erasesize can however be zero. But checking if erasesize is
> zero beforehands does not fix the situation. Or am I missing
> something?
It doesn't just check for zero, it checks a couple other things
including if erasesize > UINT_MAX.
regards,
dan carpenter
WARNING: multiple messages have this Message-ID (diff)
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Joern Engel <joern@lazybastard.org>,
yangerkun <yangerkun@huawei.com>,
Richard Weinberger <richard@nod.at>,
Vignesh Raghavendra <vigneshr@ti.com>,
linux-mtd@lists.infradead.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mtd: phram: Prevent divide by zero bug in phram_setup()
Date: Fri, 21 Jan 2022 14:51:03 +0300 [thread overview]
Message-ID: <20220121115103.GH1978@kadam> (raw)
In-Reply-To: <20220121121748.24e98015@xps13>
On Fri, Jan 21, 2022 at 12:17:48PM +0100, Miquel Raynal wrote:
> Hi Dan,
>
> dan.carpenter@oracle.com wrote on Fri, 21 Jan 2022 08:38:36 +0300:
>
> > The problem is that "erasesize" is a uint32_t type so it might be
>
> Don't you mean uint64_t here? Otherwise I don't get the sentence.
>
Yeah. I meant uint64_t. Will resend.
> > non-zero but the truncated "(uint32_t)erasesize" value *is* zero. That
>
> s/*is*/*can* be/ ? (again, if my understanding is correct).
>
It might be a situation where "erasesize" is non-zero but after we
truncated it "(uint32_t)erasesize" is zero.
> > would lead to the divide by zero bug.
> >
> > Avoid the bug by delaying the divide until after we have validated
> > that "erasesize" is reasonable.
>
> I don't really get the fix. If "erasesize" is big enough, then
> (uint32_t)erasesize can however be zero. But checking if erasesize is
> zero beforehands does not fix the situation. Or am I missing
> something?
It doesn't just check for zero, it checks a couple other things
including if erasesize > UINT_MAX.
regards,
dan carpenter
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next prev parent reply other threads:[~2022-01-21 11:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-21 5:38 [PATCH] mtd: phram: Prevent divide by zero bug in phram_setup() Dan Carpenter
2022-01-21 5:38 ` Dan Carpenter
2022-01-21 11:17 ` Miquel Raynal
2022-01-21 11:17 ` Miquel Raynal
2022-01-21 11:51 ` Dan Carpenter [this message]
2022-01-21 11:51 ` Dan Carpenter
2022-01-22 2:43 ` yangerkun
2022-01-22 2:43 ` yangerkun
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