From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 70A32C9830D for ; Fri, 25 Sep 2026 07:31:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id E7BB710F90F; Fri, 25 Sep 2026 07:30:50 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=gmail.com header.i=@gmail.com header.b="eJuC4NkO"; dkim-atps=neutral Received: from mail-pj2-f13.google.com (mail-pj2-f13.google.com [74.125.227.141]) by gabe.freedesktop.org (Postfix) with ESMTPS id 54C2310E960 for ; Thu, 24 Sep 2026 06:44:37 +0000 (UTC) Received: by mail-pj2-f13.google.com with SMTP id 98e67ed59e1d1-398c066106cso1032596a91.1 for ; Wed, 23 Sep 2026 23:44:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1790232277; x=1790837077; darn=lists.freedesktop.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=lbB99fzKqqncd9v0PrpyQHGW/pl7V8ppi+GHfHAQQBo=; b=eJuC4NkOEPqY3kYYu1NXFhqU9E+hrefJ97e0cXgbyU8DcGzM2bdJufAuQ9B7MsiS0U PDronVwK55YOjMjIrsrkpB2IrppxFFLl5RethLrovdy/YLXNCLDIpPfaWjGgWD9A/qkP xAtmDwbE3sdGWEduMCdS8/GeRepDom5RbOwxBnQ0oLfXEHzx1SDpDWcdMkgeu2OSduz7 qc0hiyJOh2G04qvR4uwUAl9xdqhd1dgwqXX5JUJx68PDwBMCMdPEn7rynMjjH+XaSG2o GZQphP9jf1tn/4MmsRopnSyWJQ9RTKtlx5mZbwFZorkxUMl6jdwR9GikrC2hKwsxI7Ba FsUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790232277; x=1790837077; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=lbB99fzKqqncd9v0PrpyQHGW/pl7V8ppi+GHfHAQQBo=; b=C3dq1mczGD7CQ0DrlnAI8nERfyiDmhXo2vneUZvXQklrClB4uwDxhDePQjIjvN7pTy GakBeD130AvPNCQ6MwzB1yvwAXduKQgGv0cmeDDlYvZfgJWjejCrRnVckRlGD+QeBvve AoBt+s15Hp2S0VfMMUqoB3mRN6H8+D6JADKhlHOnBrcYfnckubjTlNnDiM4g7hO4v2LQ nPikhLOi0zcOdwn4bJrhjmn2Q/JWd9O2euYiSBmsVvwnTzzh7tASdsumiYcqKsQFVU3V bBq9Wk4aCC8yLkhhKleGxw+VEXeUnVpAWs+QKI68wSOnieL2QrMy68XvZm04jEK4HfYf 9Aqw== X-Gm-Message-State: AFuF++kUENsS8VxDaVwIFDq3/a16V8hoEG+dWxSu2AoGasIubrgl5NVX gKU6Ta+UNOR9hFpQLGJhz6AMtTHLn8n56F0ybMGyzJZSjfeNOCMz9q0F X-Gm-Gg: AYBFou12vwGQDncwFPQs72JgQeFWD1vyiO8DieCvKyQKKQ/kJ2sMLlWJHyBbRwumjQN wBE1gzEOMbZMQGmRBzydhvtOKqZXN05CuSyuYQkw8SMfzbwLNoJ9SDdCDYWwgxBnIg0pSfF2iZy AfrXHGrtC8xsgeze2jsIzloR0qBIeoYq69qJmYkx2vYu9R0p5V/3pDpoUp7lxW9CwW+ztWebqEh fzCijjG23+/syd+MPcw4Eqb3L7+6IgawJa7lbRYwVbrvtTpAOBMCA7L4ktgq0ob3mIOBeyarsKJ NbRnvLNstnh9GoPD5YS3aeW+8buBXmEEoG5h+ZF8gQiazbhyQDbsbCE7rwUECSJDEnbsMTmzGbY Q7lCiTLiKKn3SpA1qujb9eqXgXlfE1cXRJuZS8Ow8XM2j2U0y02GpDDhyxxOHpXjcdtwq1HC7hs UdbHWIwjWCUH+seN1TGHg1UMtDOc8EpWTn45zugxw2dQAFWUm2haw3E3NfTWP24iPLdJEPctHb+ r6Cr+qVZ5ltat+v2aMje8k1OKykGF8G5xJxpjVkVLGawxZRYWlZ9KjcKLwc2HI/G3PywcFYD8ln NdtnrI6Ygw== X-Received: by 2002:a17:90a:d603:b0:39e:6c68:1550 with SMTP id 98e67ed59e1d1-3a098969ba9mr1148247a91.24.1790232276784; Wed, 23 Sep 2026 23:44:36 -0700 (PDT) Received: from phui-2.c.googlers.com.com (67.51.127.34.bc.googleusercontent.com. [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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Mailman-Approved-At: Fri, 25 Sep 2026 07:30:44 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" 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 != 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 != 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 = 1 and stored stale read_buff[1] data into the EDID buffer; whereas with this fix applied, ret != 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, unsigned 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 != 2) { ret = -EIO; drm_err(dev, "Read EDID byte %zu failed\n", i); goto err_drm_dev_exit; -- 2.55.0.1082.g2b9226bbc0-goog