Commit Message
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?
Phil
Comments
On 06/19/2017 02:18 PM, Phil Blundell wrote:
> Here's a patch that fixes bug 20874 for me, fwiw. It still passes
> "make subdirs='resolv' xcheck".
>
> OK to commit?
How hard would it be to write a test case for this? We also need a
ChangeLog entry.
Thanks,
Florian
On Mon, 2017-06-26 at 17:35 +0200, Florian Weimer wrote:
> How hard would it be to write a test case for this? We also need a
> ChangeLog entry.
It's a race, so a testcase is always going to be a bit hit-and-miss.
But something similar to the example from the original bug report would
probably show it up fairly reliably. I'll see what I can do.
I did include a changelog entry when I resent the patch this afternoon
though you're right that I forgot it earlier.
I think I also ought to run the testcase under valgrind for a while to
convince myself a bit more thoroughly that it's OK.
Thanks
Phil
On 06/26/2017 11:41 AM, Phil Blundell wrote:
> On Mon, 2017-06-26 at 17:35 +0200, Florian Weimer wrote:
>> How hard would it be to write a test case for this? We also need a
>> ChangeLog entry.
>
> It's a race, so a testcase is always going to be a bit hit-and-miss.
> But something similar to the example from the original bug report would
> probably show it up fairly reliably. I'll see what I can do.
Even if it is unreliably the result is that we have a false-positive and
that IMO is OK from a regression testing standpoint. If we ever see the
test fail it would indicate an incomplete fix and that's important
information.
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(-)
@@ -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;
--
2.11.0