gai_cancel()

  On Mon, 2017-06-19 at 13:18 +0100, Phil Blundell wrote:
> On Mon, 2017-06-19 at 12:04 +0100, Phil Blundell wrote:
> > Under conditions that I don't entirely understand yet, we seem to 
> > be somehow returning from gai_suspend while its waitlist[] entry is
> > still linked into requestlist->waiting. 
> 
> Here's a patch that fixes bug 20874 for me, fwiw.  It still passes
> "make subdirs='resolv' xcheck". 
> 
> OK to commit?

Ping?

2017-06-26  Phil Blundell  <pb@pbcl.net>

	* resolv/gai_suspend.c (gai_suspend): Ensure we always remove the
	entry we added to the waitlist before returning.

From 6e5dbbcfc0594dad90dc6f8b4537dba26bceb428 Mon Sep 17 00:00:00 2001
From: Phil Blundell <pb@pbcl.net>
Date: Mon, 19 Jun 2017 13:11:00 +0100
Subject: [PATCH] gai_suspend: Remove bogus check for EAI_INPROGRESS [BZ
 #20874]

If we added an entry to the waitlist for any request, it is important
that we remove it again before returning.  Failing to do so will
cause obscure and hard-to-debug crashes because the linked list
will contain a pointer to a struct that was assigned on the stack
and has since been overwritten.

Although we check that the current "return value" of the request
is EAI_INPROGRESS before adding an entry to its waitlist, this
value may change while we sleep so we cannot assume it will still
be EAI_INPROGRESS when we come to remove the entry afterwards.
---
 resolv/gai_suspend.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
  

On Jun 26 2017, Phil Blundell <pb@pbcl.net> wrote:

> diff --git a/resolv/gai_suspend.c b/resolv/gai_suspend.c
> index a86bd4360d..139d636c78 100644
> --- a/resolv/gai_suspend.c
> +++ b/resolv/gai_suspend.c
> @@ -111,8 +111,7 @@ gai_suspend (const struct gaicb *const list[], int ent,
>        /* Now remove the entry in the waiting list for all requests
>  	 which didn't terminate.  */
>        for (cnt = 0; cnt < ent; ++cnt)
> -	if (list[cnt] != NULL && list[cnt]->__return == EAI_INPROGRESS
> -	    && requestlist[cnt] != NULL)
> +	if (list[cnt] != NULL && requestlist[cnt] != NULL)
>  	  {
>  	    struct waitlist **listp = &requestlist[cnt]->waiting;

Is the comment still accurate?

Andreas.