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Message-ID: <20211023103158.GA4145@titan>
Date: Sat, 23 Oct 2021 12:31:58 +0200
From: Len Baker <len.baker@....com>
To: Matthew Wilcox <willy@...radead.org>
Cc: Len Baker <len.baker@....com>,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
Iurii Zaikin <yzaikin@...gle.com>,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-hardening@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sysctl: Avoid open coded arithmetic in memory allocator
functions
Hi Matthew,
On Sat, Oct 16, 2021 at 05:18:24PM +0100, Matthew Wilcox wrote:
> On Sat, Oct 16, 2021 at 05:28:28PM +0200, Len Baker wrote:
> > +static size_t new_dir_size(size_t namelen)
> > +{
> > + size_t bytes;
> > +
> > + if (check_add_overflow(sizeof(struct ctl_dir), sizeof(struct ctl_node),
> > + &bytes))
> > + return SIZE_MAX;
> > + if (check_add_overflow(bytes, array_size(sizeof(struct ctl_table), 2),
> > + &bytes))
> > + return SIZE_MAX;
> > + if (check_add_overflow(bytes, namelen, &bytes))
> > + return SIZE_MAX;
> > + if (check_add_overflow(bytes, (size_t)1, &bytes))
> > + return SIZE_MAX;
> > +
> > + return bytes;
> > +}
>
> I think this is overkill. All these structs are small and namelen is
> supplied by the kernel, not specified by userspace. It really complicates
> the code, and I don't see the advantage.
>
Ok, understood. I will send a v2 without this function.
Thanks for the review,
Len
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