Attachment 6813 Details for Bug 8409 – Patch

[patch] Patch

look (text/plain), 2.27 KB, created by Volker Lendecke on 2011-08-26 15:33:00 UTC

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Creator: Volker Lendecke

Created: 2011-08-26 15:33:00 UTC

Size: 2.27 KB

patch

obsolete

>From 1bc64508d08566f26ac98414cbd5a5f8749221a5 Mon Sep 17 00:00:00 2001
>From: Volker Lendecke <vl@samba.org>
>Date: Fri, 26 Aug 2011 16:54:18 +0200
>Subject: [PATCH] s3: Fix a winbind race leading to 100% CPU
>
>This fixes a race condition that leads to the winbindd_children list becoming
>corrupted. It happens when on a busy winbind SIGCHLD is a bit late.
>
>Imagine a winbind with multiple requests in the queue for a single child. Child
>dies, and before the SIGCHLD handler is called we find the socket to be dead.
>wb_child_request_done is called, receiving an error from wb_simple_trans_recv.
>It closes the socket. Then immediately the wb_child_request_trigger will do
>another fork_domain_child before the signal handler is called. This means that
>we do another fork_domain_child, we have child->sock==-1 at this point.
>fork_domain_child will do a DLIST_ADD(winbindd_children, child) a second time
>where the child is already part of that list. This corrupts the list. Then the
>signal handler kicks in, spinning in
>
>for (child = winbindd_children; child != NULL; child = child->next) {
>
>forever. Not good. This patch makes sure that both conditions (sock==-1 and not
>part of the list) for a winbindd_child struct match up.
>---
> source3/winbindd/winbindd_dual.c |    5 +++--
> 1 files changed, 3 insertions(+), 2 deletions(-)
>
>diff --git a/source3/winbindd/winbindd_dual.c b/source3/winbindd/winbindd_dual.c
>index 1078f8d..0b4cc6e 100644
>--- a/source3/winbindd/winbindd_dual.c
>+++ b/source3/winbindd/winbindd_dual.c
>@@ -43,6 +43,8 @@
> extern bool override_logfile;
> extern struct winbindd_methods cache_methods;
> 
>+static struct winbindd_child *winbindd_children = NULL;
>+
> /* Read some data from a client connection */
> 
> static NTSTATUS child_read_request(struct winbindd_cli_state *state)
>@@ -171,6 +173,7 @@ static void wb_child_request_done(struct tevent_req *subreq)
> 		 */
> 		close(state->child->sock);
> 		state->child->sock = -1;
>+		DLIST_REMOVE(winbindd_children, state->child);
> 		tevent_req_error(req, err);
> 		return;
> 	}
>@@ -489,8 +492,6 @@ void setup_child(struct winbindd_domain *domain, struct winbindd_child *child,
> 	SMB_ASSERT(child->binding_handle != NULL);
> }
> 
>-static struct winbindd_child *winbindd_children = NULL;
>-
> void winbind_child_died(pid_t pid)
> {
> 	struct winbindd_child *child;
>-- 
>1.7.4.1
>

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jra: review+

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Attachments on bug 8409: 6813