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bh=v5Jk2Zg/jlnzRSMuz3x0o8u6pgBwywiIWqNlylIDzik=; b=FJP4qh95Kbu7zw26XluYKyrhAzkUwwlYyfNwTNiNcTTqTP8F/XXU35UWacDuPTJjweoYEL GiYjvWHc3hP69mR6Nd8Y0X0WY1MhVMAE0YigfhdKbkDTFm6Yu3ty06aWvtNuFAP7d/DjX7 07kNGOCCR7yu9HNPPsuBlqObJA+bm99wZDIvMY+LYOn7+NsuVHHfCklCayId2CpF6Y4Z7q CyRux8QYr/Z54JvD/4L9g9CK7j7Dvj1objxwbKHwaSMbZC9vELYTo7Un6BxICoGvKpQ3// pVIe7usTj7Dk0FeyvXGdhXTmYPjK4+X/EGYWZzhO1tyN32ChRI3QEgTDofZlSg== Date: Thu, 3 Feb 2022 10:46:54 +0100 From: Miquel Raynal To: Richard Weinberger Cc: =?UTF-8?B?TWljaGHFgiBLxJlwaWXFhA==?= , Vignesh Raghavendra , Boris Brezillon , linux-mtd , linux-kernel Subject: Re: [PATCH v3 4/4] mtdchar: add MEMREAD ioctl Message-ID: <20220203104654.6cb43ea3@xps13> In-Reply-To: <1173246756.12597.1643879936765.JavaMail.zimbra@nod.at> References: <20220125104822.8420-1-kernel@kempniu.pl> <20220125104822.8420-5-kernel@kempniu.pl> <1173246756.12597.1643879936765.JavaMail.zimbra@nod.at> Organization: Bootlin X-Mailer: Claws Mail 3.17.7 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Richard, richard@nod.at wrote on Thu, 3 Feb 2022 10:18:56 +0100 (CET): > Micha=C5=82, >=20 > ----- Urspr=C3=BCngliche Mail ----- > > Von: "Micha=C5=82 K=C4=99pie=C5=84" > > An: "Miquel Raynal" , "richard" , "Vignesh Raghavendra" > > CC: "Boris Brezillon" , "linux-mtd" , "linux-kernel" > > > > Gesendet: Dienstag, 25. Januar 2022 11:48:22 > > Betreff: [PATCH v3 4/4] mtdchar: add MEMREAD ioctl =20 >=20 > > + if (req.start + req.len > mtd->size) { =20 >=20 > I think this can overflow since both req.start and req.len are u64. > So an evil-doer might bypass this check. >=20 > > + ret =3D -EINVAL; > > + goto out; > > + } > > + > > + datbuf_len =3D min_t(size_t, req.len, mtd->erasesize); > > + if (datbuf_len > 0) { > > + datbuf =3D kmalloc(datbuf_len, GFP_KERNEL); =20 >=20 > If mtd->erasesize is large (which is not uncommon these days) you might > request more from kmalloc() than it can serve. > Maybe kvmalloc() makes more sense? Mmmh, I would really like these buffers dma-able. I just discovered mtd_kmalloc_up_to(). Would this work? >=20 > > + if (!datbuf) { > > + ret =3D -ENOMEM; > > + goto out; > > + } > > + } > > + > > + oobbuf_len =3D min_t(size_t, req.ooblen, mtd->erasesize); > > + if (oobbuf_len > 0) { > > + oobbuf =3D kmalloc(oobbuf_len, GFP_KERNEL); =20 >=20 > Same. >=20 > Thanks, > //richard Thanks, Miqu=C3=A8l