Commit 8ea93928 authored Oct 12, 2015 by Ian Abbott Committed by Greg Kroah-Hartman Oct 13, 2015

staging: comedi: avoid bad truncation of a size_t in comedi_read()



At one point in `comedi_read()`, the variable `n` gets assigned to the
minimum of the parameter `nbytes` and the amount of readable buffer
space `m`.  The way that is done currently is unsafe in the unlikely
case that `nbytes` exceeds `UINT_MAX`, so fix it.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 76e8e7d4

drivers/staging/comedi/comedi_fops.c

+1 −4

Original line number	Diff line number	Diff line
		@@ -2493,13 +2493,10 @@ static ssize_t comedi_read(struct file file, char __user buf, size_t nbytes,
		while (nbytes > 0 && !retval) {
		set_current_state(TASK_INTERRUPTIBLE);

		n = nbytes;

		m = comedi_buf_read_n_available(s);
		if (async->buf_read_ptr + m > async->prealloc_bufsz)
		m = async->prealloc_bufsz - async->buf_read_ptr;
		if (m < n)
		n = m;
		n = min_t(size_t, m, nbytes);

		if (n == 0) {
		unsigned runflags = comedi_get_subdevice_runflags(s);

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