From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f200.google.com (mail-oi1-f200.google.com [209.85.167.200]) (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 178533AEF3A for ; Fri, 31 Jul 2026 08:09:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785485398; cv=none; b=VvRVXGzO13su2nc303Ymp8W5RmPfRAzwmBdBUZQ5rCtwQrpFoOOtd94r7msFJ4RcMupCIbTRBa1R/8Wgtq6kBqRifC4Zs4LuORAKSRzdOv+EVM/fu7yQxzXxeBYDUsits89MQd6oUwAqaCRs103o2jQuJoTp0CLn09go9HnhQ9M= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785485398; c=relaxed/simple; bh=Imf69LJHeq6cUyM/YKUDzCje+INyNqOjm6swjJyAF8Y=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; b=GILE8rfQBSJ2VedxjSmsHdfBOqA8Tamx+AsGjSF6E444dMmIBU4Y+36Fmu9UKYPbCYn1Z2PdjGqNJLyhdwD9Jpayk+CodRrvU0N+7ELPhjp54KjTErI0JPg5GBe8+Ii+CRd/LvzXJVxxzhWjs/223uanmZLu0tgfkUletQPXSVs= 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=209.85.167.200 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-f200.google.com with SMTP id 5614622812f47-4ab8b646492so1229298b6e.0 for ; Fri, 31 Jul 2026 01:09:56 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785485396; x=1786090196; 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=hcLXGnGBArC4eUmaSD6XHmSX9gaXT72dQWcvdoPv4a4=; b=qL9BSwk69AQwImXnSP2qnP+KwvO7EANGVRKFLH7BIAtOJm5kqUfM2LJuee0HTqtuOc SLFOVj78+H7+i4BIAId4mp0Zoo6befn7yWt3kqYOlmCmTl0PejN/B256mMhjTUE8csST SinMfUcucfwRsi3lmsQjD08KQB5lP2Ow3aLOpmcdYjPcf0Vruny68HLCW32U7wr8ij9w mrsPgDX9pE2jftO+X7HAfIO3+x5BYjsAb2yMKvTrWZI0Ka+TCH8PHwWw/XSgXrswxHzc B1DKtUsA/M71x3tNinksLNphS2m1XhGVZ3xkdAeQjs1dhGhpsBGAC+ldTsqkv9O2xXq+ 4hSg== X-Gm-Message-State: AOJu0YxCUTji1I4u3/blVjCKoXRf1H9vWMw/4HGpYLzHRTgCFG5Qq9xn gaLkNhtxh0HflQuu0Vx4wiptA3dChvXPRCSo6LSh94d+aSnx/pUThAupd5y0+NgvocqFa7scXJm 5pTVtosWdAui+hfGIemSNsTXBCgsaErqQ31sHHKc4tst3+MG/tHwMs6Q5BHY= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:148a:b0:492:3ed0:9073 with SMTP id 5614622812f47-4ae4c4d50bbmr978635b6e.4.1785485395879; Fri, 31 Jul 2026 01:09:55 -0700 (PDT) Date: Fri, 31 Jul 2026 01:09:55 -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: <6a6c5853.1b55b669.19788.001a.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 in 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"), including the fix direction, but it was never applied to ep_open() itself. Fix it as originally suggested: add an inode back-pointer to ep_data, have destroy_ep_files() clear inode->i_private to NULL under dev->lock before the object can be freed, and have ep_open() read inode->i_private and pin the result with get_ep() under that same lock, bailing out with -ENOENT if it finds NULL. This makes liveness self-evident at the point of use instead of being inferred from device state, so it holds regardless of which path frees the endpoint. gadgetfs_create_file() gains an optional inode-out parameter so activate_ep_files() can capture the inode it creates; the ep0 caller in gadgetfs_fill_super() passes NULL, since dev_data is unaffected by this fix. 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 | 51 +++++++++++++++++++++---------- 1 file changed, 35 insertions(+), 16 deletions(-) diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c index d87a8ab51510..f566b2ec7c38 100644 --- a/drivers/usb/gadget/legacy/inode.c +++ b/drivers/usb/gadget/legacy/inode.c @@ -207,6 +207,7 @@ struct ep_data { struct usb_endpoint_descriptor desc, hs_desc; struct list_head epfiles; wait_queue_head_t wait; + struct inode *inode; }; static inline void get_ep (struct ep_data *data) @@ -235,6 +236,7 @@ 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 +819,39 @@ 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); + data = inode->i_private; + if (data == NULL) { + spin_unlock_irq (&dev->lock); + return -ENOENT; + } + 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; } @@ -1563,6 +1579,7 @@ static void destroy_ep_files (struct dev_data *dev) /* break link to FS */ ep = list_first_entry (&dev->epfiles, struct ep_data, epfiles); list_del_init (&ep->epfiles); + ep->inode->i_private = NULL; spin_unlock_irq (&dev->lock); /* break link to controller */ @@ -1588,7 +1605,8 @@ static void destroy_ep_files (struct dev_data *dev) static int gadgetfs_create_file (struct super_block *sb, char const *name, - void *data, const struct file_operations *fops); + void *data, const struct file_operations *fops, + struct inode **inode_out); static int activate_ep_files (struct dev_data *dev) { @@ -1618,7 +1636,7 @@ static int activate_ep_files (struct dev_data *dev) goto enomem1; err = gadgetfs_create_file (dev->sb, data->name, - data, &ep_io_operations); + data, &ep_io_operations, &data->inode); if (err) goto enomem2; list_add_tail (&data->epfiles, &dev->epfiles); @@ -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) { @@ -1984,7 +2000,7 @@ gadgetfs_make_inode (struct super_block *sb, * so inode and dentry are paired, until device reconfig. */ static int gadgetfs_create_file (struct super_block *sb, char const *name, - void *data, const struct file_operations *fops) + void *data, const struct file_operations *fops, struct inode **inode_out) { struct dentry *dentry; struct inode *inode; @@ -1994,6 +2010,9 @@ static int gadgetfs_create_file (struct super_block *sb, char const *name, if (!inode) return -ENOMEM; + if(inode_out) + *inode_out = inode; + dentry = simple_start_creating(sb->s_root, name); if (IS_ERR(dentry)) { iput(inode); @@ -2056,7 +2075,7 @@ gadgetfs_fill_super (struct super_block *sb, struct fs_context *fc) goto Enomem; dev->sb = sb; - rc = gadgetfs_create_file(sb, CHIP, dev, &ep0_operations); + rc = gadgetfs_create_file(sb, CHIP, dev, &ep0_operations, NULL); if (rc) { put_dev(dev); goto Enomem; -- 2.43.0