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authorJann Horn <jannh@google.com>2018-07-06 17:12:56 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-07-17 11:37:52 +0200
commit0fdef3142f99430b94f5d394ca2b181d20d87e77 (patch)
treef4acf07425fc28c6e0f3e1b26ae43812f9655a09
parent7e7c86d2757067f52fa1a81f5d472f5662bd0e7f (diff)
downloadlinux-linaro-stable-0fdef3142f99430b94f5d394ca2b181d20d87e77.tar.gz
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. 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>
-rw-r--r--drivers/usb/misc/yurex.c23
1 files changed, 6 insertions, 17 deletions
diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c
index 54e53ac4c08f..f36968ee2e70 100644
--- a/drivers/usb/misc/yurex.c
+++ b/drivers/usb/misc/yurex.c
@@ -406,8 +406,7 @@ 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;
@@ -415,26 +414,16 @@ 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,