On Tue, Jan 14, 2020 at 01:22:07PM -0800, Linus Torvalds wrote:
> The fact is, copying a string from user space is *very* different from
> copying a fixed number of bytes, and that whole dance with
>
> max_addr = user_addr_max();
>
> is absolutely required and necessary.
>
> You completely broke string copying.
BTW, a quick grep through the callers has found something odd -
static ssize_t kmemleak_write(struct file *file, const char __user *user_buf,
size_t size, loff_t *ppos)
{
char buf[64];
int buf_size;
int ret;
buf_size = min(size, (sizeof(buf) - 1));
if (strncpy_from_user(buf, user_buf, buf_size) < 0)
return -EFAULT;
buf[buf_size] = 0;
What the hell? If somebody is calling write(fd, buf, n) they'd
better be ready to see any byte from buf[0] up to buf[n - 1]
fetched, and if something is unmapped - deal with -EFAULT.
Is something really doing that and if so, why does kmemleak
try to accomodate that idiocy?
The same goes for several more ->write() instances - mtrr_write(),
armada_debugfs_crtc_reg_write() and cio_ignore_write(); IMO that's
seriously misguided (and cio one ought use vmemdup_user() instead
of what it's doing)...
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