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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0972efa0bsm2960830a91.8.2026.09.23.23.44.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 23:44:36 -0700 (PDT) From: Hui Peng To: jani.nikula@linux.intel.com, tzimmermann@suse.de, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hui Peng Subject: [PATCH v2 1/2] drm/udl: reject short USB control transfers in udl_read_edid_block() Date: Thu, 24 Sep 2026 06:44:33 +0000 Message-ID: <20260924064434.2541959-2-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.310.g51773c2048-goog In-Reply-To: <20260924064434.2541959-1-benquike@gmail.com> References: <20260919223511.3889061-1-benquike@gmail.com> <20260924064434.2541959-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In udl_read_edid_block(), usb_control_msg() requests 2 bytes into read_buff for each EDID byte, and read_buff[1] is stored into buf[i]. Currently the short-transfer check tests ret < 1 instead of ret !=3D 2, so if a short USB control transfer returns 1 byte, read_buff[1] is not written by usb_control_msg() and retains the previous iteration's byte (or uninitialized kmalloc(2) memory on the first iteration), which is then copied into buf[i]. Change the check from ret < 1 to ret !=3D 2 so any short USB control transfer fails with -EIO. Tested in QEMU against Linux 7.3.0-rc3 using dummy_hcd and raw-gadget emulating a DisplayLink UDL USB device: on the unfixed kernel, when usb_control_msg() returned 1 byte for an EDID read (short transfer), udl_read_edid_block() accepted ret =3D 1 and stored stale read_buff[1] data into the EDID buffer; whereas with this fix applied, ret !=3D 2 correctly fails with -EIO and prevents EDID buffer corruption. Fixes: 5320918b9a87 ("drm/udl: initial UDL driver (v4)") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng --- Changes in v2: - Split out as patch 1/2 as requested by Jani Nikula. - Added testing details in QEMU on short USB EDID control transfers. drivers/gpu/drm/udl/udl_edid.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/udl/udl_edid.c b/drivers/gpu/drm/udl/udl_edid.c index af4cff2a7c51..b7c462436573 100644 --- a/drivers/gpu/drm/udl/udl_edid.c +++ b/drivers/gpu/drm/udl/udl_edid.c @@ -36,7 +36,7 @@ static int udl_read_edid_block(void *data, u8 *buf, unsig= ned int block, size_t l if (ret < 0) { drm_err(dev, "Read EDID byte %zu failed err %x\n", i, ret); goto err_drm_dev_exit; - } else if (ret < 1) { + } else if (ret !=3D 2) { ret =3D -EIO; drm_err(dev, "Read EDID byte %zu failed\n", i); goto err_drm_dev_exit; --=20 2.55.0.1082.g2b9226bbc0-goog From nobody Thu Sep 24 12:53:02 2026 Received: from mail-pj2-f12.google.com (mail-pj2-f12.google.com [74.125.227.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D3B0940B110 for ; 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[34.127.51.67]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0972efa0bsm2960830a91.8.2026.09.23.23.44.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Sep 2026 23:44:36 -0700 (PDT) From: Hui Peng To: jani.nikula@linux.intel.com, tzimmermann@suse.de, maarten.lankhorst@linux.intel.com, mripard@kernel.org, airlied@gmail.com, simona@ffwll.ch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Hui Peng Subject: [PATCH v2 2/2] drm/udl: clean up USB resources if drm_dev_register() fails Date: Thu, 24 Sep 2026 06:44:34 +0000 Message-ID: <20260924064434.2541959-3-benquike@gmail.com> X-Mailer: git-send-email 2.56.0.rc1.310.g51773c2048-goog In-Reply-To: <20260924064434.2541959-1-benquike@gmail.com> References: <20260919223511.3889061-1-benquike@gmail.com> <20260924064434.2541959-1-benquike@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In udl_usb_probe(), udl_driver_create() calls udl_init(udl), which allocates USB URBs and DMA buffers via udl_alloc_urb_list() that are normally freed by udl_drop_usb() in udl_usb_disconnect(). If drm_dev_register() fails in udl_usb_probe(), udl_usb_probe() returns without calling udl_drop_usb(udl), leaking the allocated URB list and DMA buffers because udl_usb_disconnect() is not called when probe fails. Call udl_drop_usb(udl) when drm_dev_register() fails in udl_usb_probe(). Tested in QEMU against Linux 7.3.0-rc3 using dummy_hcd by simulating a registration error in drm_dev_register(): on the unfixed kernel, udl_usb_probe() returned an error without calling udl_drop_usb(udl), leaking 8 allocated URBs and DMA buffers; whereas with this fix applied, udl_drop_usb(udl) is called on error, freeing all URB and DMA allocations. Fixes: 5320918b9a87 ("drm/udl: initial UDL driver (v4)") Cc: stable@vger.kernel.org Assisted-by: LLM Signed-off-by: Hui Peng Reviewed-by: Thomas Zimmermann --- Changes in v2: - Split out as patch 2/2 as requested by Jani Nikula. - Added testing details in QEMU on drm_dev_register() failure cleanup. drivers/gpu/drm/udl/udl_drv.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c index 1922988625eb..239a6983f49f 100644 --- a/drivers/gpu/drm/udl/udl_drv.c +++ b/drivers/gpu/drm/udl/udl_drv.c @@ -97,8 +97,10 @@ static int udl_usb_probe(struct usb_interface *interface, return PTR_ERR(udl); =20 r =3D drm_dev_register(&udl->drm, 0); - if (r) + if (r) { + udl_drop_usb(udl); return r; + } =20 DRM_INFO("Initialized udl on minor %d\n", udl->drm.primary->index);