Commit 591c5f8a authored by Ian Abbott's avatar Ian Abbott Committed by Greg Kroah-Hartman

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

At one point in `comedi_write()`, the variable `n` gets assigned to the
minimum of the parameter `nbytes` and the amount of writeable buffer
space.  The way that is done currently is unsafe in the unlikely case
that `nbytes` exceeds `UINT_MAX`, so fix it.
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Reviewed-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 84a185ec
......@@ -2357,16 +2357,13 @@ static ssize_t comedi_write(struct file *file, const char __user *buf,
break;
}
n = nbytes;
m = n;
if (async->buf_write_ptr + m > async->prealloc_bufsz)
m = async->prealloc_bufsz - async->buf_write_ptr;
/* Allocate all free buffer space. */
comedi_buf_write_alloc(s, async->prealloc_bufsz);
if (m > comedi_buf_write_n_allocated(s))
m = comedi_buf_write_n_allocated(s);
if (m < n)
n = m;
/* Avoid buffer wraparound. */
if (async->buf_write_ptr + m > async->prealloc_bufsz)
m = async->prealloc_bufsz - async->buf_write_ptr;
n = min_t(size_t, m, nbytes);
if (n == 0) {
if (file->f_flags & O_NONBLOCK) {
......
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