[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] chardev: fix pty_chr_timer
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-devel] [PATCH] chardev: fix pty_chr_timer |
Date: |
Thu, 22 Aug 2013 13:10:04 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130806 Thunderbird/17.0.8 |
On 08/22/13 11:57, Gerd Hoffmann wrote:
> pty_chr_timer first calls pty_chr_update_read_handler(), then clears
> timer_tag (because it is a one-shot timer). This is the wrong order
> though. pty_chr_update_read_handler might re-arm time timer, and the
> new timer_tag gets overwitten in that case.
>
> This leads to crashes when unplugging a pty chardev: pty_chr_close
> thinks no timer is running -> timer isn't canceled -> pty_chr_timer gets
> called with stale CharDevState -> BOOM.
>
> This patch fixes the ordering.
> Kill the pointless goto while being at it.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=994414
>
> Signed-off-by: Gerd Hoffmann <address@hidden>
> ---
> qemu-char.c | 12 ++++--------
> 1 file changed, 4 insertions(+), 8 deletions(-)
>
> diff --git a/qemu-char.c b/qemu-char.c
> index 1be1cf6..1621fbd 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -1026,15 +1026,11 @@ static gboolean pty_chr_timer(gpointer opaque)
> struct CharDriverState *chr = opaque;
> PtyCharDriver *s = chr->opaque;
>
> - if (s->connected) {
> - goto out;
> - }
> -
> - /* Next poll ... */
> - pty_chr_update_read_handler(chr);
> -
> -out:
> s->timer_tag = 0;
> + if (!s->connected) {
> + /* Next poll ... */
> + pty_chr_update_read_handler(chr);
> + }
> return FALSE;
> }
pty_chr_timer()
s->timer_tag = 0;
pty_chr_update_read_handler() // s->connected == 0
pty_chr_state(..., 1) // G_IO_HUP is clear
not calling: g_source_remove(s->timer_tag)
s->connected = 1;
qemu_chr_be_generic_open()
s->fd_tag = io_add_watch_poll()
So, in this order, s->timer_tag is not removed in pty_chr_state().
But that shouldn't be necessary anyway, since pty_chr_timer() returns
FALSE, and its associated tag (s->timer_tag, see pty_chr_rearm_timer())
is removed anyway.
Seems OK to me.
Reviewed-by: Laszlo Ersek <address@hidden>