From b95dd4cdfd327b5121beb2c6b45b07b96d11f538 Mon Sep 17 00:00:00 2001 From: Ben Hutchings Date: Wed, 15 Aug 2018 21:45:37 +0100 Subject: [PATCH] USB: yurex: Check for truncation in yurex_read() [ Upstream commit 14427b86837a4baf1c121934c6599bdb67dfa9fc ] snprintf() always returns the full length of the string it could have printed, even if it was truncated because the buffer was too small. So in case the counter value is truncated, we will over-read from in_buffer and over-write to the caller's buffer. I don't think it's actually possible for this to happen, but in case truncation occurs, WARN and return -EIO. Signed-off-by: Ben Hutchings Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/usb/misc/yurex.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/usb/misc/yurex.c b/drivers/usb/misc/yurex.c index e36c6c6452cd..1e672343bcd6 100644 --- a/drivers/usb/misc/yurex.c +++ b/drivers/usb/misc/yurex.c @@ -423,6 +423,9 @@ static ssize_t yurex_read(struct file *file, char __user *buffer, size_t count, spin_unlock_irqrestore(&dev->lock, flags); mutex_unlock(&dev->io_mutex); + if (WARN_ON_ONCE(len >= sizeof(in_buffer))) + return -EIO; + return simple_read_from_buffer(buffer, count, ppos, in_buffer, len); }