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Message-ID: <72a444cd42629f5bdd56647e7aa24588d6964bec.camel@redhat.com>
Subject: Re: [PATCH v2 1/5] string.h: add array-wrappers for (v)memdup_user()
From:   Philipp Stanner <pstanner@redhat.com>
To:     Dan Carpenter <dan.carpenter@linaro.org>
Cc:     Kees Cook <keescook@chromium.org>,
        Andy Shevchenko <andy@kernel.org>,
        Eric Biederman <ebiederm@xmission.com>,
        Christian Brauner <brauner@kernel.org>,
        David Disseldorp <ddiss@suse.de>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Siddh Raman Pant <code@siddh.me>,
        Nick Alcock <nick.alcock@oracle.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>, Zack Rusin <zackr@vmware.com>,
        VMware Graphics Reviewers 
        <linux-graphics-maintainer@vmware.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        kexec@lists.infradead.org, linux-hardening@vger.kernel.org,
        David Airlie <airlied@redhat.com>
Date:   Mon, 18 Sep 2023 11:13:48 +0200
In-Reply-To: <b219788a-69e6-44cf-a609-91f9640967f5@moroto.mountain>
References: <cover.1694202430.git.pstanner@redhat.com>
         <93001a9f3f101be0f374080090f9c32df73ca773.1694202430.git.pstanner@redhat.com>
         <b219788a-69e6-44cf-a609-91f9640967f5@moroto.mountain>
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On Sat, 2023-09-16 at 17:32 +0300, Dan Carpenter wrote:
> On Fri, Sep 08, 2023 at 09:59:40PM +0200, Philipp Stanner wrote:
> > +static inline void *memdup_array_user(const void __user *src,
> > size_t n, size_t size)
> > +{
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0size_t nbytes;
> > +
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (unlikely(check_mul_overf=
low(n, size, &nbytes)))
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0return ERR_PTR(-EOVERFLOW);
>=20
> No need for an unlikely() because check_mul_overflow() already has
> one
> inside.

ACK. I overlooked that as it was hidden in the callstack.


> =C2=A0 I feel like -ENOMEM is more traditional but I doubt
> anyone/userspace
> cares.

I agree with Andy here. We're not allocating, so -ENOMEM makes no sense
IMO.


P.

>=20
> > +
> > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0return memdup_user(src, nbyt=
es);
> > +}
>=20
> regards,
> dan carpenter
>=20