USB: CVE-2018-16276

USB: yurex: fix out-of-bounds uaccess in read handler

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2018-16276
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=90f2a76ccd37cce2530df49335bcea6cd0e23797

Change-Id: Ie5e54d7049bd414a22d458364f2965ccc6ca8e3d
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

1 files changed, 75 insertions, 0 deletions

diff --git a/patches/cve/CVE-2018-16276-USB-yurex-fix-out-of-bounds-uaccess-in-read-handler.patch b/patches/cve/CVE-2018-16276-USB-yurex-fix-out-of-bounds-uaccess-in-read-handler.patch
new file mode 100644
index 0000000..62b5e11
--- /dev/null
+++ b/patches/cve/CVE-2018-16276-USB-yurex-fix-out-of-bounds-uaccess-in-read-handler.patch
@@ -0,0 +1,75 @@
+From 90f2a76ccd37cce2530df49335bcea6cd0e23797 Mon Sep 17 00:00:00 2001
+From: Jann Horn <jannh@google.com>
+Date: Fri, 6 Jul 2018 17:12:56 +0200
+Subject: [PATCH] USB: yurex: fix out-of-bounds uaccess in read handler
+
+commit f1e255d60ae66a9f672ff9a207ee6cd8e33d2679 upstream.
+
+In general, accessing userspace memory beyond the length of the supplied
+buffer in VFS read/write handlers can lead to both kernel memory corruption
+(via kernel_read()/kernel_write(), which can e.g. be triggered via
+sys_splice()) and privilege escalation inside userspace.
+
+Fix it by using simple_read_from_buffer() instead of custom logic.
+
+CVE: CVE-2018-16276
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=90f2a76ccd37cce2530df49335bcea6cd0e23797]
+
+Fixes: 6bc235a2e24a ("USB: add driver for Meywa-Denki & Kayac YUREX")
+Signed-off-by: Jann Horn <jannh@google.com>
+Cc: stable <stable@vger.kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ drivers/usb/misc/yurex.c | 23 ++++++-----------------
+ 1 file changed, 6 insertions(+), 17 deletions(-)
+
+diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
+index 58abdf28620a..47763311a42e 100644
+--- a/drivers/usb/misc/yurex.c
++++ b/drivers/usb/misc/yurex.c
+@@ -400,8 +400,7 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
+                          loff_t *ppos)
+ {
+        struct usb_yurex *dev;
+-       int retval = 0;
+-       int bytes_read = 0;
++       int len = 0;
+        char in_buffer[20];
+        unsigned long flags;
+ 
+@@ -409,26 +408,16 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count,
+ 
+        mutex_lock(&dev->io_mutex);
+        if (!dev->interface) {          /* already disconnected */
+-               retval = -ENODEV;
+-               goto exit;
++               mutex_unlock(&dev->io_mutex);
++               return -ENODEV;
+        }
+ 
+        spin_lock_irqsave(&dev->lock, flags);
+-       bytes_read = snprintf(in_buffer, 20, "%lld\n", dev->bbu);
++       len = snprintf(in_buffer, 20, "%lld\n", dev->bbu);
+        spin_unlock_irqrestore(&dev->lock, flags);
+-
+-       if (*ppos < bytes_read) {
+-               if (copy_to_user(buffer, in_buffer + *ppos, bytes_read - *ppos))
+-                       retval = -EFAULT;
+-               else {
+-                       retval = bytes_read - *ppos;
+-                       *ppos += bytes_read;
+-               }
+-       }
+-
+-exit:
+        mutex_unlock(&dev->io_mutex);
+-       return retval;
++
++       return simple_read_from_buffer(buffer, count, ppos, in_buffer, len);
+ }
+ 
+ static ssize_t yurex_write(struct file *file, const char __user *user_buffer,
+-- 
+2.20.1
+