From: Sandy Harris <sandyinchina@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH 1/8] Replace memset() with memzero_explicit()
Date: Wed, 17 Nov 2021 11:08:45 +0800 [thread overview]
Message-ID: <CACXcFm=bPdoLqYHEUpeZEQEULVGW6ej4ESHX+vMdeGfvjc51tg@mail.gmail.com> (raw)
In-Reply-To: <YZObImtJITs1ZfUc@kroah.com>
On Tue, Nov 16, 2021 at 7:51 PM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> Have you looked at the output of the compiler to see if this really is
> needed or not?
No. To do that right you'd need to look at (at least) gcc & clang,
multiple architectures (cross-compiled & native) & various levels
of optimisation. I just looked at the C code.
> And what exactly are you zeroing out that could be read afterward
> somehow?
Whatever it is, the person who wrote the code thought it was
worth zeroing out with memset(). The only question is whether
it is safer to use memzero_explicit().
Granted in many cases this will not matter unless the kernel
is compiled at some optimisation level that does cross-function
analysis so it might be "smart" enough to optimise out the
memset(). Also granted it does not matter unless an attacker
can look inside the running kernel & if he or she has that
level of privilege, then you have much else to worry about.
Still, it seemed safer to me to use memzero_explicit() in
these cases.
next prev parent reply other threads:[~2021-11-17 3:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-16 11:25 [PATCH 1/8] Replace memset() with memzero_explicit() Sandy Harris
2021-11-16 11:49 ` Greg Kroah-Hartman
2021-11-16 11:50 ` Greg Kroah-Hartman
2021-11-16 12:52 ` Greg Kroah-Hartman
2021-11-17 3:08 ` Sandy Harris [this message]
2021-11-17 6:01 ` Greg Kroah-Hartman
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