diff options
| author | Ilya Zykov <ilya@ilyx.ru> | 2013-03-04 23:19:41 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-06-11 12:04:21 -0700 |
| commit | a1843e9577d2bf2aea6c439be3bfa5038299e079 (patch) | |
| tree | 2664137ce7970a9dc7fd9e840c0de461ad964333 | |
| parent | f84f26e72c1286582da55dd76752ef4296faeccd (diff) | |
tty: Correct tty buffer flush.
commit 64325a3be08d364a62ee8f84b2cf86934bc2544a upstream.
The root of problem is carelessly zeroing pointer(in function __tty_buffer_flush()),
when another thread can use it. It can be cause of "NULL pointer dereference".
Main idea of the patch, this is never free last (struct tty_buffer) in the active buffer.
Only flush the data for ldisc(buf->head->read = buf->head->commit).
At that moment driver can collect(write) data in buffer without conflict.
It is repeat behavior of flush_to_ldisc(), only without feeding data to ldisc.
Signed-off-by: Ilya Zykov <ilya@ilyx.ru>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/tty_buffer.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c index 6c9b7cd6778a..4f02f9ce05c5 100644 --- a/drivers/tty/tty_buffer.c +++ b/drivers/tty/tty_buffer.c @@ -114,11 +114,14 @@ static void __tty_buffer_flush(struct tty_struct *tty) { struct tty_buffer *thead; - while ((thead = tty->buf.head) != NULL) { - tty->buf.head = thead->next; - tty_buffer_free(tty, thead); + if (tty->buf.head == NULL) + return; + while ((thead = tty->buf.head->next) != NULL) { + tty_buffer_free(tty, tty->buf.head); + tty->buf.head = thead; } - tty->buf.tail = NULL; + WARN_ON(tty->buf.head != tty->buf.tail); + tty->buf.head->read = tty->buf.head->commit; } /** |