tmakin/ack-tegra
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

tty: n_tty: use uint for space returned by tty_write_room()

Browse Source 
[ Upstream commit d97aa066678bd1e2951ee93db9690835dfe57ab6 ]

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 03b3b1a240 ("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>
Link: https://lore.kernel.org/r/20250317070046.24386-6-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Jiri Slaby (SUSE)
2025-03-17 08:00:20 +01:00
committed by Greg Kroah-Hartman
parent 1817c4b850
commit 5b2b692804
1 changed files with 7 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/tty/n_tty.c
View File

@@ -486,7 +486,8 @@ 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);
@@ -522,16 +523,16 @@ 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;
@@ -696,7 +697,7 @@ 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;