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From: William Kucharski <william.kucharski@oracle.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Keith Busch <keith.busch@intel.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	YueHaibing <yuehaibing@huawei.com>,
	linux-mm@kvack.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mm/gup_benchmark: prevent integer overflow in ioctl
Date: Thu, 01 Nov 2018 08:28:55 +0000	[thread overview]
Message-ID: <E7641C0F-C619-4054-BD14-685E8D448F49@oracle.com> (raw)
In-Reply-To: <20181101071613.7x3smxwz5wo57n2m@mwanda>



> On Nov 1, 2018, at 1:16 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 
> My patch lets people allocate 4MB.  (U32_MAX / 4096 * sizeof(void *)).
> Surely, that's enough?  I liked my check because it avoids the divide so
> it's faster and it is a no-op on 64bit systems.

It should be enough, and you're right, it does avoid extra math.

However, in that case I'd like to see a comment added so that anyone looking
at the code in the future knows why you limited the allocation to ULONG_MAX
bytes.

Thanks,
    William Kucharski

WARNING: multiple messages have this Message-ID (diff)
From: William Kucharski <william.kucharski@oracle.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Keith Busch <keith.busch@intel.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Kees Cook <keescook@chromium.org>,
	YueHaibing <yuehaibing@huawei.com>,
	linux-mm@kvack.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mm/gup_benchmark: prevent integer overflow in ioctl
Date: Thu, 1 Nov 2018 02:28:55 -0600	[thread overview]
Message-ID: <E7641C0F-C619-4054-BD14-685E8D448F49@oracle.com> (raw)
In-Reply-To: <20181101071613.7x3smxwz5wo57n2m@mwanda>



> On Nov 1, 2018, at 1:16 AM, Dan Carpenter <dan.carpenter@oracle.com> wrote:
> 
> My patch lets people allocate 4MB.  (U32_MAX / 4096 * sizeof(void *)).
> Surely, that's enough?  I liked my check because it avoids the divide so
> it's faster and it is a no-op on 64bit systems.

It should be enough, and you're right, it does avoid extra math.

However, in that case I'd like to see a comment added so that anyone looking
at the code in the future knows why you limited the allocation to ULONG_MAX
bytes.

Thanks,
    William Kucharski

  reply	other threads:[~2018-11-01  8:28 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-25  6:15 [PATCH] mm/gup_benchmark: prevent integer overflow in ioctl Dan Carpenter
2018-10-25  6:15 ` Dan Carpenter
2018-10-25  7:32 ` Kirill A. Shutemov
2018-10-25  7:32   ` Kirill A. Shutemov
2018-11-01  6:38 ` William Kucharski
2018-11-01  6:38   ` William Kucharski
2018-11-01  7:16   ` Dan Carpenter
2018-11-01  7:16     ` Dan Carpenter
2018-11-01  8:28     ` William Kucharski [this message]
2018-11-01  8:28       ` William Kucharski

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