From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6B3A22590 for ; Sun, 22 Jan 2023 15:25:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD30FC433D2; Sun, 22 Jan 2023 15:25:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1674401112; bh=bHn+98W+LRqJXZsz4t28zbYdG3ANip8pqUSeTp+aJaA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uYd6BWivnCP2Iz7Q0mqSi9490nMmlwTNoKS1+PGvcrCPugyroP7EnLFcCTmuVUoqu B/HSg2Jd94TkECQk/AY4REISkpqoCCuTh/lFfPKKaCJNj4z3N9WzD9/g5dc07aO9YJ D3yYPZdQxpbedl6BxbBcqARU2zMu20LymJe/ifAY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Felipe Balbi , Lorenzo Colitti , Carlos Llamas , =?UTF-8?q?Maciej=20=C5=BBenczykowski?= , stable Subject: [PATCH 6.1 114/193] usb: gadget: f_ncm: fix potential NULL ptr deref in ncm_bitrate() Date: Sun, 22 Jan 2023 16:04:03 +0100 Message-Id: <20230122150251.542054172@linuxfoundation.org> X-Mailer: git-send-email 2.39.1 In-Reply-To: <20230122150246.321043584@linuxfoundation.org> References: <20230122150246.321043584@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Maciej Żenczykowski commit c6ec929595c7443250b2a4faea988c62019d5cd2 upstream. In Google internal bug 265639009 we've received an (as yet) unreproducible crash report from an aarch64 GKI 5.10.149-android13 running device. AFAICT the source code is at: https://android.googlesource.com/kernel/common/+/refs/tags/ASB-2022-12-05_13-5.10 The call stack is: ncm_close() -> ncm_notify() -> ncm_do_notify() with the crash at: ncm_do_notify+0x98/0x270 Code: 79000d0b b9000a6c f940012a f9400269 (b9405d4b) Which I believe disassembles to (I don't know ARM assembly, but it looks sane enough to me...): // halfword (16-bit) store presumably to event->wLength (at offset 6 of struct usb_cdc_notification) 0B 0D 00 79 strh w11, [x8, #6] // word (32-bit) store presumably to req->Length (at offset 8 of struct usb_request) 6C 0A 00 B9 str w12, [x19, #8] // x10 (NULL) was read here from offset 0 of valid pointer x9 // IMHO we're reading 'cdev->gadget' and getting NULL // gadget is indeed at offset 0 of struct usb_composite_dev 2A 01 40 F9 ldr x10, [x9] // loading req->buf pointer, which is at offset 0 of struct usb_request 69 02 40 F9 ldr x9, [x19] // x10 is null, crash, appears to be attempt to read cdev->gadget->max_speed 4B 5D 40 B9 ldr w11, [x10, #0x5c] which seems to line up with ncm_do_notify() case NCM_NOTIFY_SPEED code fragment: event->wLength = cpu_to_le16(8); req->length = NCM_STATUS_BYTECOUNT; /* SPEED_CHANGE data is up/down speeds in bits/sec */ data = req->buf + sizeof *event; data[0] = cpu_to_le32(ncm_bitrate(cdev->gadget)); My analysis of registers and NULL ptr deref crash offset (Unable to handle kernel NULL pointer dereference at virtual address 000000000000005c) heavily suggests that the crash is due to 'cdev->gadget' being NULL when executing: data[0] = cpu_to_le32(ncm_bitrate(cdev->gadget)); which calls: ncm_bitrate(NULL) which then calls: gadget_is_superspeed(NULL) which reads ((struct usb_gadget *)NULL)->max_speed and hits a panic. AFAICT, if I'm counting right, the offset of max_speed is indeed 0x5C. (remember there's a GKI KABI reservation of 16 bytes in struct work_struct) It's not at all clear to me how this is all supposed to work... but returning 0 seems much better than panic-ing... Cc: Felipe Balbi Cc: Lorenzo Colitti Cc: Carlos Llamas Cc: stable@vger.kernel.org Signed-off-by: Maciej Żenczykowski Cc: stable Link: https://lore.kernel.org/r/20230117131839.1138208-1-maze@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_ncm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/drivers/usb/gadget/function/f_ncm.c +++ b/drivers/usb/gadget/function/f_ncm.c @@ -83,7 +83,9 @@ static inline struct f_ncm *func_to_ncm( /* peak (theoretical) bulk transfer rate in bits-per-second */ static inline unsigned ncm_bitrate(struct usb_gadget *g) { - if (gadget_is_superspeed(g) && g->speed >= USB_SPEED_SUPER_PLUS) + if (!g) + return 0; + else if (gadget_is_superspeed(g) && g->speed >= USB_SPEED_SUPER_PLUS) return 4250000000U; else if (gadget_is_superspeed(g) && g->speed == USB_SPEED_SUPER) return 3750000000U;