@@ -488,7 +488,8 @@ static int do_output_char(u8 c, struct tty_struct *tty, int space)
static int process_output(u8 c, struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
- int space, retval;
+ unsigned int space;
+ int retval;
mutex_lock(&ldata->output_lock);
@@ -524,16 +525,16 @@ static ssize_t process_output_block(struct tty_struct *tty,
const u8 *buf, unsigned int nr)
{
struct n_tty_data *ldata = tty->disc_data;
- int space;
- int i;
+ unsigned int space;
+ int i;
const u8 *cp;
mutex_lock(&ldata->output_lock);
space = tty_write_room(tty);
- if (space <= 0) {
+ if (space == 0) {
mutex_unlock(&ldata->output_lock);
- return space;
+ return 0;
}
if (nr > space)
nr = space;
@@ -698,7 +699,7 @@ static int n_tty_process_echo_ops(struct tty_struct *tty, size_t *tail,
static size_t __process_echoes(struct tty_struct *tty)
{
struct n_tty_data *ldata = tty->disc_data;
- int space, old_space;
+ unsigned int space, old_space;
size_t tail;
u8 c;
tty_write_room() returns an "unsigned int". So in case some insane driver (like my tty test driver) returns (legitimate) UINT_MAX from its tty_operations::write_room(), n_tty is confused on several places. For example, in process_output_block(), the result of tty_write_room() is stored into (signed) "int". So this UINT_MAX suddenly becomes -1. And that is extended to ssize_t and returned from process_output_block(). This causes a write() to such a node to receive -EPERM (which is -1). Fix that by using proper "unsigned int" and proper "== 0" test. And return 0 constant directly in that "if", so that it is immediately clear what is returned ("space" equals to 0 at that point). Similarly for process_output() and __process_echoes(). Note this does not fix any in-tree driver as of now. If you want "Fixes: something", it would be commit 03b3b1a2405c ("tty: make tty_operations::write_room return uint"). I intentionally do not mark this patch by a real tag below. Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org> --- drivers/tty/n_tty.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)