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[149.14.88.26]) by smtp.gmail.com with ESMTPSA id b16-20020a05600010d000b0031aef72a021sm11830334wrx.86.2023.09.18.02.13.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 18 Sep 2023 02:13:49 -0700 (PDT) Message-ID: <72a444cd42629f5bdd56647e7aa24588d6964bec.camel@redhat.com> Subject: Re: [PATCH v2 1/5] string.h: add array-wrappers for (v)memdup_user() From: Philipp Stanner To: Dan Carpenter Cc: Kees Cook , Andy Shevchenko , Eric Biederman , Christian Brauner , David Disseldorp , Luis Chamberlain , Siddh Raman Pant , Nick Alcock , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Daniel Vetter , Zack Rusin , VMware Graphics Reviewers , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-hardening@vger.kernel.org, David Airlie Date: Mon, 18 Sep 2023 11:13:48 +0200 In-Reply-To: References: <93001a9f3f101be0f374080090f9c32df73ca773.1694202430.git.pstanner@redhat.com> User-Agent: Evolution 3.48.4 (3.48.4-1.fc38) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org 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