Hi all,

small program below crashes on read() from driverfs file:

int main(void)
{
	int fd, ret;
	char buf[16];

	fd = open("/var/driver/root/pci0/status", 0);
	ret = read(fd, buf, sizeof(buf));
	close(fd);
}

it's because driverfs_read_file() function blindly uses entry->show()
return value without sanity check. As a result userspace process requested 
16 bytes, but got ~45 and smashed stack as a bonus. You can also get this 
effect pressing F3 in Midnight Commander on driverfs files.

Attached patch adds check that returned value is less then requested 
byte count. I know that actual callback function device_read_status()
should also be fixed, but I found this bug after midnight and 
decided to sleep a little :)

Best regards.

-- 
Andrey Panin            | Embedded systems software engineer
pazke@orbita1.ru        | PGP key: wwwkeys.eu.pgp.net