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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46c1ee0189esm25128520f8f.9.2026.06.26.04.31.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2026 04:31:41 -0700 (PDT) Date: Fri, 26 Jun 2026 12:31:39 +0100 From: David Laight To: Christian =?UTF-8?B?S8O2bmln?= Cc: Yousef Alhouseen , Gerd Hoffmann , Vivek Kasireddy , Sumit Semwal , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dma-buf: udmabuf: avoid list copy size overflow Message-ID: <20260626123139.7d6ec6ec@pumpkin> In-Reply-To: <06bddfca-d868-4043-ac6f-28ca103fff02@amd.com> References: <20260624125242.11232-1-alhouseenyousef@gmail.com> <06bddfca-d868-4043-ac6f-28ca103fff02@amd.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wed, 24 Jun 2026 14:58:58 +0200 Christian K=C3=B6nig wrote: > On 6/24/26 14:52, Yousef Alhouseen wrote: > > UDMABUF_CREATE_LIST copies an array whose element count comes from > > userspace. The count is compared against list_limit, but list_limit is a > > signed module parameter while the count is u32. =20 >=20 > We should probably just drop the sign from the module parameter instead. Does anything sanity-check the module parameter? David >=20 > I don't see an use case for negative values here. >=20 > Regards, > Christian. >=20 > >=20 > > If the limit is raised too far or made negative, that comparison no > > longer bounds the count to a range where sizeof(*list) * count fits in > > the u32 temporary used for the copy length. A wrapped copy length lets > > memdup_user() copy fewer entries than udmabuf_create() subsequently > > walks, leading to out-of-bounds reads from the copied list. > >=20 > > Take a positive snapshot of the module limit and use memdup_array_user() > > so the multiplication is checked before copying. > >=20 > > Signed-off-by: Yousef Alhouseen > > --- > > drivers/dma-buf/udmabuf.c | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > >=20 > > diff --git a/drivers/dma-buf/udmabuf.c b/drivers/dma-buf/udmabuf.c > > index bced421c0..b4078ec84 100644 > > --- a/drivers/dma-buf/udmabuf.c > > +++ b/drivers/dma-buf/udmabuf.c > > @@ -469,14 +469,15 @@ static long udmabuf_ioctl_create_list(struct file= *filp, unsigned long arg) > > struct udmabuf_create_list head; > > struct udmabuf_create_item *list; > > int ret =3D -EINVAL; > > - u32 lsize; > > + int limit; > >=20 > > if (copy_from_user(&head, (void __user *)arg, sizeof(head))) > > return -EFAULT; > > - if (head.count > list_limit) > > + limit =3D READ_ONCE(list_limit); > > + if (!head.count || limit <=3D 0 || head.count > limit) > > return -EINVAL; > > - lsize =3D sizeof(struct udmabuf_create_item) * head.count; > > - list =3D memdup_user((void __user *)(arg + sizeof(head)), lsize= ); > > + list =3D memdup_array_user((void __user *)(arg + sizeof(head)), > > + head.count, sizeof(*list)); > > if (IS_ERR(list)) > > return PTR_ERR(list); > >=20 > > -- > > 2.54.0 > > =20 >=20 >=20