From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) (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 C583019F121 for ; Fri, 31 Jul 2026 04:45:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785473102; cv=none; b=cp3AyPHnlfRHRLCkaUZt4mLBDeoLFsax2CFqb0pnc2B7rnmjFpniO5tWuNXmU6SnCRiyGzZmcPK7oJ2FmlpWy2ipHfk5ljtEbqb8Dcvf9QDfakNwI7BdQg/iPh5liWRgLpbQZtHf505lsZxp9CvSw+TqARtq+nxTj2BUU4kzsqg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785473102; c=relaxed/simple; bh=uBEld1HNESMAw0clOEKZUUksFibrpUxibwlb+qliAco=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=ExgzPq2ugz5raqpimnDfC/YoiV7kxacZqWZUVees19xeneJzcKmdxydxOc8H6MXZdeVu/Y8YHrJsBB/tXf1VBDCeGtTS7b+dTPo9A5/lim9OpTfAWJ7K8uQqdpmkQSguhcgT8lsbIUFHLIvxLQMdFaqZWFRtxiic+lOf7zhccGw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f198.google.com with SMTP id 5614622812f47-495b0cf250dso441644b6e.3 for ; Thu, 30 Jul 2026 21:45:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785473099; x=1786077899; h=content-type:to:from:subject:message-id:in-reply-to:date :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to:content-type; bh=cUf3GpRV/4+DzfBPmUtjJnsgAC/c8ss/J7DR8oCzmzI=; b=cLDOWjTKT7ajgT/vgWKbp7vst+sq+JDu/Hj96T6KC4CjAynyO66UIe6Kn12pj6JCXS edT7MzzL/Sio+YGJEhGOzuVZVWU27+crak6PYJxLUJGSuB3SGVMIg7QFGZGY9gpDYIQs JPVaFF6zrMJAvwW68d0Bn91ltBjc4FrcvT2bpRrzwMt1Y33awc10Cwii3CBDrzwJW3mN RXDDLThvbXp3a49KZ5cfDlhCQ7urrHOWRT7BuJZORdT4S2tlelaffy/x6XM5Np/rc2I4 UtoyvVB1hBGL0p35NuPgTL5ynBrDT/4uTzWTFlCDc6+zAQef1Z9KuBN5ruxUPAVFjK/D OPOQ== X-Gm-Message-State: AOJu0YyiuBKjazL0npawSkJmgipBn9NNmFrskpI2EHDrILman1kQ8wDG HoCKgTyO1oBFjfMf/XZGtoGOCACo8Ol0dqzfDAQW2MG3BhiRr6Y/TBuI/fMh7tH+XkF2aIL+Wea YYrO8wEZCtAAH1lH7MnI4kx2Khs9/5RusDm30N1EpDf7t0JPDjU7uqQK5SAQ= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:23cb:b0:49b:c387:36da with SMTP id 5614622812f47-4ae4c6b06a0mr389275b6e.25.1785473099654; Thu, 30 Jul 2026 21:44:59 -0700 (PDT) Date: Thu, 30 Jul 2026 21:44:59 -0700 In-Reply-To: <6a6bfa43.1b55b669.19788.0016.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a6c284b.5cf34cee.28a846.0006.GAE@google.com> Subject: Forwarded: [PATCH] usb: gadgetfs: fix use-after-free in ep_open() From: syzbot To: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" For archival purposes, forwarding an incoming command email to linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com. *** Subject: [PATCH] usb: gadgetfs: fix use-after-free in ep_open() Author: kartikey406@gmail.com #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci ep_open() dereferenced inode->i_private and locked its embedded mutex before checking whether the underlying ep_data was still alive. destroy_ep_files(), called from gadgetfs_unbind(), can free that same ep_data concurrently, since nothing prevented an in-flight open() from racing the teardown. KASAN reports a slab-use-after-free read inside __mutex_lock_common() from ep_open(), with the object freed by a concurrent gadgetfs_unbind() -> destroy_ep_files() -> put_ep() -> kfree(). This race was identified by Al Viro on LKML in 2006 ("races in drivers/usb/gadget/inode.c") but never fixed in ep_open() itself. Fix it by checking dev->state and reading inode->i_private only under dev->lock, and pinning the result with get_ep() before dev->lock is dropped and before data->lock is touched. dev is reached via the file-scope singleton the_device, which stays valid for the duration of any open() in progress, so no dereference of ep_data happens before its liveness is confirmed. This depends on dev->state being set to STATE_DEV_UNBOUND under dev->lock before destroy_ep_files() is called. gadgetfs_unbind() already does this; activate_ep_files()'s enomem0 cleanup path did not, leaving the same race open on the bind-failure path. This patch adds the missing state transition there too. Reported-by: syzbot+df9e891bf8ea586f846b@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=df9e891bf8ea586f846b Signed-off-by: Deepanshu Kartikey --- drivers/usb/gadget/legacy/inode.c | 40 +++++++++++++++++++++---------- 1 file changed, 28 insertions(+), 12 deletions(-) diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index d87a8ab51510..0d0989d79020 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -235,6 +235,7 @@ static void put_ep (struct ep_data *data) static const char *CHIP; static DEFINE_MUTEX(sb_mutex); /* Serialize superblock operations */ +static struct dev_data *the_device; /*----------------------------------------------------------------------*/ @@ -817,25 +818,39 @@ ep_config (struct ep_data *data, const char *buf, size_t len) static int ep_open (struct inode *inode, struct file *fd) { - struct ep_data *data = inode->i_private; - int value = -EBUSY; + struct dev_data *dev = the_device; + struct ep_data *data; + int value = -ENODEV; + + spin_lock_irq (&dev->lock); + if (dev->state == STATE_DEV_UNBOUND) { + spin_unlock_irq (&dev->lock); + return -ENOENT; + } + data = inode->i_private; + get_ep (data); + spin_unlock_irq (&dev->lock); - if (mutex_lock_interruptible(&data->lock) != 0) + if (mutex_lock_interruptible(&data->lock) != 0) { + put_ep (data); return -EINTR; - spin_lock_irq (&data->dev->lock); - if (data->dev->state == STATE_DEV_UNBOUND) + } + + value = -EBUSY; + spin_lock_irq (&dev->lock); + if (dev->state == STATE_DEV_UNBOUND) value = -ENOENT; else if (data->state == STATE_EP_DISABLED) { value = 0; data->state = STATE_EP_READY; - get_ep (data); fd->private_data = data; - VDEBUG (data->dev, "%s ready\n", data->name); + VDEBUG (dev, "%s ready\n", data->name); } else - DBG (data->dev, "%s state %d\n", - data->name, data->state); - spin_unlock_irq (&data->dev->lock); + DBG (dev, "%s state %d\n", data->name, data->state); + spin_unlock_irq (&dev->lock); mutex_unlock(&data->lock); + if (value) + put_ep (data); return value; } @@ -1632,6 +1647,9 @@ static int activate_ep_files (struct dev_data *dev) kfree (data); enomem0: DBG (dev, "%s enomem\n", __func__); + spin_lock_irq (&dev->lock); + dev->state = STATE_DEV_UNBOUND; + spin_unlock_irq (&dev->lock); destroy_ep_files (dev); return -ENOMEM; } @@ -1663,8 +1681,6 @@ gadgetfs_unbind (struct usb_gadget *gadget) put_dev (dev); } -static struct dev_data *the_device; - static int gadgetfs_bind(struct usb_gadget *gadget, struct usb_gadget_driver *driver) { -- 2.43.0