This is a note to let you know that I've just added the patch titled
tty: Correct tty buffer flush.
to the 3.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tty-correct-tty-buffer-flush.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 689901ce9cedd2d34a5404dda146d0604cbc2a5e Mon Sep 17 00:00:00 2001
From: Ilya Zykov <ilya@xxxxxxx>
Date: Mon, 4 Mar 2013 23:19:41 +0400
Subject: tty: Correct tty buffer flush.
From: Ilya Zykov <ilya@xxxxxxx>
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@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Rui Xiang <rui.xiang@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/tty_buffer.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
--- a/drivers/tty/tty_buffer.c
+++ b/drivers/tty/tty_buffer.c
@@ -114,11 +114,14 @@ static void __tty_buffer_flush(struct tt
{
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;
}
/**
Patches currently in stable-queue which might be from ilya@xxxxxxx are
queue-3.4/tty-correct-tty-buffer-flush.patch
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