From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7BC8F494807; Mon, 31 Aug 2026 14:06:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788185165; cv=none; b=mIWhBUKwf0nKG/vwQ305ghTv+kxRog/zV25ZGYyY2R2VPtXsrrSIkcA707VuKO4wS/wpDHmQHGrlp6SJuguQpE2tVO49/TakgTIUH1yt1+Aj3Kd4l+ojrZu4HyPO1f2UlJ7UZUpVMsxslxRngEsX/WaliNhwgVTnLUUN6jw4dH8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788185165; c=relaxed/simple; bh=uPz/QihLj1b10N1w1gL+drDzwzY56IVz7zQgyXHaPOU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Rj6wtO1JgAgesSMCp5sAl/u9BW2bFNh2Mn6QlNKb3TwdatGJr3ctj+H9JcQtd7KASNsir21nO51DzWpvNXIPsuFM6RoItqGT+r/OpD1aQmusRVCwU+OlVhZ22PFEeuPkXTJc1d4Qc7rq/nu+FGQC7AuAcW05SNZhM+v2eT8ch4I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RWgAsKTu; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="RWgAsKTu" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0EA371F000E9; Mon, 31 Aug 2026 14:06:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1788185164; bh=YWbbl7BUmUAb8mW6C6kIuxVhWdJLiSyse2ntLVE6ryk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RWgAsKTu7+XtJjaBrvleamqs5dMKs8Y1M9TOViDKnlK77XZ8D/NY5IdDDExtqnr0m hrzDDg8AUkP0cxUCva6AFIoOP1dEXYEJxX7ukYBc/uB6GAbBaQTXL+BJB2isns1zG7 sfGzYi2PFmbVrNz+pHJSXsHCySRfZflp/CgNq/20= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Miguel=20Pe=C3=B1aranda?= , Alan Stern Subject: [PATCH 5.15 69/69] usb: usbfs: fix use-after-free of usb_device in usbdev_release() Date: Mon, 31 Aug 2026 15:35:42 +0200 Message-ID: <20260831133402.202024907@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260831133358.601894154@linuxfoundation.org> References: <20260831133358.601894154@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore 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 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Miguel Peñaranda commit 0dd68b5d01d022fc9c5e71c82a82b0a94d3d0671 upstream. usbdev_release() drops its reference to the struct usb_device before draining the list of completed async URBs, but that drain path reads back through the same object: free_async() calls dec_usb_memory_use_count() for any URB whose buffer came from the usbfs mmap() region, and its first statement is bus_to_hcd(ps->dev->bus). After a disconnect the usbfs reference can be the last one, in which case usb_put_dev() frees the device and the subsequent loop reads offset 80 of freed memory and uses the result as a struct usb_hcd *, which hcd_buffer_free_pages() then dereferences. This is reachable by an unprivileged process that has read/write access to a /dev/bus/usb node: mmap() the fd, submit one URB with a buffer inside the mapping, wait for the device to be unplugged, then munmap() and close(). It reproduces on every attempt rather than being a race, because a live MAP_SHARED vma holds a reference on the struct file, so usbdev_release() cannot run until the last vma is gone and the freeing branch of dec_usb_memory_use_count() is always taken. BUG: KASAN: slab-use-after-free in dec_usb_memory_use_count+0x3ae/0x410 Read of size 8 at addr ffff8880122ee050 by task poc/769 CPU: 1 UID: 1000 PID: 769 Comm: poc Tainted: G B 6.12.94 #3 Call Trace: dec_usb_memory_use_count+0x3ae/0x410 free_async+0x2aa/0x4f0 usbdev_release+0x375/0x460 __fput+0x3ea/0xb50 __x64_sys_close+0x86/0x100 Allocated by task 11: usb_alloc_dev+0x55/0xd90 hub_event+0x2524/0x43d0 Freed by task 769: kfree+0x121/0x360 device_release+0xd2/0x280 usb_put_dev+0x23/0x30 usbdev_release+0x2d8/0x460 Release the device reference after the drain loop instead. Nothing between the two points requires it to have been dropped. Fixes: f7d34b445abc ("USB: Add support for usbfs zerocopy.") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-5 Signed-off-by: Miguel Peñaranda Reviewed-by: Alan Stern Link: https://patch.msgid.link/20260810121209.795089-1-mig.penaranda07@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/devio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -1099,7 +1099,6 @@ static int usbdev_release(struct inode * if (!ps->suspend_allowed) usb_autosuspend_device(dev); usb_unlock_device(dev); - usb_put_dev(dev); put_pid(ps->disc_pid); put_cred(ps->cred); @@ -1108,6 +1107,7 @@ static int usbdev_release(struct inode * free_async(as); as = async_getcompleted(ps); } + usb_put_dev(dev); kfree(ps); return 0;