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Subject[PATCH 5/5] tty: fix tty_line must not be equal to number of allocated tty pointers in tty driver
From: Nathael Pajani <>

I found a bug "by chance" in drivers/char/tty_io.c

I mean "by chance" because I was just reading the code of the
tty_find_polling_driver() to make a new tty_find_by_name() function.

In tty_find_polling_driver() the driver actually test "tty_line <=
p->num" while num refers to the number of struct tty_struct pointers
allocated for the p->ttys (p is a tty_driver), and tty_line is scanned
in a tty name, which can be for example ttyS2. Then tty_line equals 2.
And if p->num is 2, we have only p->ttys[0] and p->ttys[1], but no

This is actually unharmful, for tty_find_polling_driver() is used only
in drivers/serial/kgdboc.c, and there's a test over there to find a
console with a matching index, which will never happen.

This is still a bug anyway.

Signed-off-by: Nathael Pajani <>
Signed-off-by: Greg Kroah-Hartman <>
drivers/char/tty_io.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 949067a..613c852 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -355,7 +355,7 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
if (*stp == '\0')
stp = NULL;

- if (tty_line >= 0 && tty_line <= p->num && p->ops &&
+ if (tty_line >= 0 && tty_line < p->num && p->ops &&
p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
res = tty_driver_kref_get(p);
*line = tty_line;

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