From a18cd6c9b6bc73dc17e8b7e9bd07decaa8833c97 Mon Sep 17 00:00:00 2001
From: Zeng Tao <prime.zeng@hisilicon.com>
Date: Fri, 4 Sep 2020 14:37:44 +0800
Subject: [PATCH] usb: core: fix slab-out-of-bounds Read in read_descriptors
Git-commit: a18cd6c9b6bc73dc17e8b7e9bd07decaa8833c97
References: git-fixes
Patch-mainline: v5.9-rc5

The USB device descriptor may get changed between two consecutive
enumerations on the same device for some reason, such as DFU or
malicius device.
In that case, we may access the changing descriptor if we don't take
the device lock here.

The issue is reported:
https://syzkaller.appspot.com/bug?id=901a0d9e6519ef8dc7acab25344bd287dd3c7be9

Cc: stable <stable@vger.kernel.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Reported-by: syzbot+256e56ddde8b8957eabd@syzkaller.appspotmail.com
Fixes: 217a9081d8e6 ("USB: add all configs to the "descriptors" attribute")
Signed-off-by: Zeng Tao <prime.zeng@hisilicon.com>
Link: https://lore.kernel.org/r/1599201467-11000-1-git-send-email-prime.zeng@hisilicon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/usb/core/sysfs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/usb/core/sysfs.c b/drivers/usb/core/sysfs.c
index a2ca38e25e0c..8d134193fa0c 100644
--- a/drivers/usb/core/sysfs.c
+++ b/drivers/usb/core/sysfs.c
@@ -889,7 +889,11 @@ read_descriptors(struct file *filp, struct kobject *kobj,
 	size_t srclen, n;
 	int cfgno;
 	void *src;
+	int retval;
 
+	retval = usb_lock_device_interruptible(udev);
+	if (retval < 0)
+		return -EINTR;
 	/* The binary attribute begins with the device descriptor.
 	 * Following that are the raw descriptor entries for all the
 	 * configurations (config plus subsidiary descriptors).
@@ -914,6 +918,7 @@ read_descriptors(struct file *filp, struct kobject *kobj,
 			off -= srclen;
 		}
 	}
+	usb_unlock_device(udev);
 	return count - nleft;
 }
 
-- 
2.26.2