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SubjectRe: [PATCH 1/1] drivers/usb/chipidea/debuc.c: avoid out of bound read
On Fri, Apr 17, 2015 at 08:04:13AM +0200, Heinrich Schuchardt wrote:
> A string written by the user may not be zero terminated.
>
> sscanf may read memory beyond the buffer if no zero byte
> is found.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
> ---
> drivers/usb/chipidea/debug.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/chipidea/debug.c b/drivers/usb/chipidea/debug.c
> index dfb05ed..ef08af3 100644
> --- a/drivers/usb/chipidea/debug.c
> +++ b/drivers/usb/chipidea/debug.c
> @@ -88,9 +88,13 @@ static ssize_t ci_port_test_write(struct file *file, const char __user *ubuf,
> char buf[32];
> int ret;
>
> - if (copy_from_user(buf, ubuf, min_t(size_t, sizeof(buf) - 1, count)))
> + count = min_t(size_t, sizeof(buf) - 1, count);
> + if (copy_from_user(buf, ubuf, count))
> return -EFAULT;

Any reasons to change above?
>
> + /* sscanf requires a zero terminated string */
> + buf[count] = 0;
> +

I prefer using '\0'

> if (sscanf(buf, "%u", &mode) != 1)
> return -EINVAL;
>
> --
> 2.1.4
>

--

Best Regards,
Peter Chen


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