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 E83C3418A58; Tue, 21 Jul 2026 21:59:00 +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=1784671142; cv=none; b=SUH8NLj9CgBAr20P2UwP0bElqL6qgiRpVz68kaAVWL/GztGv2v0pOOcmdcYZr5ODQOYiAgm++5sTAv/P/77RqftD098DxZUExYxCL0RJTObbwIUwC3vFf8yPJhCf10MPFptSGvvTNeYqPaWIagfKIa9GmW9dt2iujkvBZN45GPI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784671142; c=relaxed/simple; bh=yrUyuozGNpT8mDyfZhHXdhWtz12i+FLCgvAjWzVxYtQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=uKHKLyDFfRb9UG51I9hEOcuI625z6saRinB8ehX+bKHentPV8yhWf0WguJ04FPMxiu6Wz1U1xEGxBYDEt0fW5Opl/H4lycikcskBYaHEKZpO7k0zZ08CLSpMR3n5Ww50ZkxkfHneYmbNZ4Hxz+n35lk0P0p0CDbY76wopDtFKOc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=RBTzl8hv; 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="RBTzl8hv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 210821F000E9; Tue, 21 Jul 2026 21:58:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784671140; bh=1jShiC+hC9NoKT8no5WOh96JUyUM5OLA6A3s39lLpME=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=RBTzl8hveH/vEKgQlFT9K1v5wJxEnSauYzD4/dTXHFrAmWcKO11BxE+vsEDpwDiT4 ndoDZlI5RlBjuPwBDz55s0v5Ej3XwCQn6ZeIgALMayx8gBM4JIKbM3FhpvIe+Loiwl yyrdAD8cLz7eLo4H+YZSAUGz9WEEVJ6Cgu3aukxk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, stable , Daniel Walker , Johan Hovold Subject: [PATCH 5.15 135/843] USB: ldusb: fix use-after-free on disconnect race Date: Tue, 21 Jul 2026 17:16:10 +0200 Message-ID: <20260721152409.053191086@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152405.946368001@linuxfoundation.org> References: <20260721152405.946368001@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-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold commit 19bdfc7b3c179331eafa423d87e1336f43bbfeb8 upstream. mutex_unlock() may access the mutex structure after releasing the lock and therefore cannot be used to manage lifetime of objects directly (unlike spinlocks and refcounts). [1][2] Use a kref to release the driver data to avoid use-after-free in mutex_unlock() when release() races with disconnect(). [1] a51749ab34d9 ("locking/mutex: Document that mutex_unlock() is non-atomic") [2] 2b9d9e0a9ba0 ("locking/mutex: Clarify that mutex_unlock(), and most other sleeping locks, can still use the lock object after it's unlocked") Fixes: ce0d7d3f575f ("usb: ldusb: ld_usb semaphore to mutex") Cc: stable Cc: Daniel Walker Signed-off-by: Johan Hovold Link: https://patch.msgid.link/20260622152612.116422-4-johan@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/misc/ldusb.c | 38 ++++++++++++++++++-------------------- 1 file changed, 18 insertions(+), 20 deletions(-) --- a/drivers/usb/misc/ldusb.c +++ b/drivers/usb/misc/ldusb.c @@ -150,6 +150,7 @@ MODULE_PARM_DESC(min_interrupt_out_inter /* Structure to hold all of our device specific stuff */ struct ld_usb { + struct kref kref; struct mutex mutex; /* locks this structure */ struct usb_interface *intf; /* save off the usb interface pointer */ unsigned long disconnected:1; @@ -201,8 +202,10 @@ static void ld_usb_abort_transfers(struc /* * ld_usb_delete */ -static void ld_usb_delete(struct ld_usb *dev) +static void ld_usb_delete(struct kref *kref) { + struct ld_usb *dev = container_of(kref, struct ld_usb, kref); + /* free data structures */ usb_free_urb(dev->interrupt_in_urb); usb_free_urb(dev->interrupt_out_urb); @@ -355,6 +358,8 @@ static int ld_usb_open(struct inode *ino goto unlock_exit; } + kref_get(&dev->kref); + /* save device in the file's private structure */ file->private_data = dev; @@ -381,17 +386,8 @@ static int ld_usb_release(struct inode * mutex_lock(&dev->mutex); - if (dev->open_count != 1) { - retval = -ENODEV; + if (dev->disconnected) goto unlock_exit; - } - if (dev->disconnected) { - /* the device was unplugged before the file was released */ - mutex_unlock(&dev->mutex); - /* unlock here as ld_usb_delete frees dev */ - ld_usb_delete(dev); - goto exit; - } /* wait until write transfer is finished */ if (dev->interrupt_out_busy) @@ -401,7 +397,7 @@ static int ld_usb_release(struct inode * unlock_exit: mutex_unlock(&dev->mutex); - + kref_put(&dev->kref, ld_usb_delete); exit: return retval; } @@ -660,6 +656,8 @@ static int ld_usb_probe(struct usb_inter dev = kzalloc(sizeof(*dev), GFP_KERNEL); if (!dev) goto exit; + + kref_init(&dev->kref); mutex_init(&dev->mutex); spin_lock_init(&dev->rbsl); dev->intf = intf; @@ -739,7 +737,7 @@ exit: return retval; error: - ld_usb_delete(dev); + kref_put(&dev->kref, ld_usb_delete); return retval; } @@ -767,18 +765,18 @@ static void ld_usb_disconnect(struct usb mutex_lock(&dev->mutex); - /* if the device is not opened, then we clean up right now */ - if (!dev->open_count) { - mutex_unlock(&dev->mutex); - ld_usb_delete(dev); - } else { - dev->disconnected = 1; + dev->disconnected = 1; + + if (dev->open_count) { /* wake up pollers */ wake_up_interruptible_all(&dev->read_wait); wake_up_interruptible_all(&dev->write_wait); - mutex_unlock(&dev->mutex); } + mutex_unlock(&dev->mutex); + + kref_put(&dev->kref, ld_usb_delete); + dev_info(&intf->dev, "LD USB Device #%d now disconnected\n", (minor - USB_LD_MINOR_BASE)); }