On 03.12.2012 13:54, Ilya Zykov wrote: > 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 release last (struct tty_buffer) in > the active buffer. > Only flush data for ldisc(tty->buf.head->read = tty->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. > Test program and bug report you can see: > https://lkml.org/lkml/2012/11/29/368 > > Cc: sta...@vger.kernel.org > Signed-off-by: Ilya Zykov <i...@ilyx.ru> > --- > diff --git a/drivers/tty/tty_buffer.c b/drivers/tty/tty_buffer.c > index 6c9b7cd..4f02f9c 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; > } > > /** >
You can include this patch, in 3.2 series , for improve stability, it would be merged in upstream 3.9-rc1. Thank you. Ilya. https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/drivers/tty/tty_buffer.c?id=64325a3be08d364a62ee8f84b2cf86934bc2544a -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
