linux-kernel - Re: [dm-devel] clone() with CLONE_NEWNET breaks kobject_uevent

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Date:	Fri, 19 Aug 2011 22:41:01 +0200
From:	Milan Broz <mbroz@...hat.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	device-mapper development <dm-devel@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kay Sievers <kay.sievers@...y.org>,
	"David S. Miller" <davem@...emloft.net>, containers@...ts.osdl.org
Subject: Re: [dm-devel] clone() with CLONE_NEWNET breaks kobject_uevent_env()

On 08/19/2011 08:39 PM, Eric W. Biederman wrote:

> But Kay's suggestion to use netlink_has_listeners() seems like good
> idea. IOW if there is no listener, it should skip quietly and not
> fail the whole call...
> In the case of ESRCH I completely agree.
>
> We are currently ignoring errors in the semantically more interesting
> case when netlink_broadcast does not deliver the packet to one of the
> listening netlink sockets.
>
> How does this patch look?
Well, your version still returns -ESRCH, so it is not helping much :-)
If you meant to handle it like I fixed in patch below (ignore ESRCH)
then I am ok with that approach, patch below fixes the problem
we have.

Thanks,
Milan

diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index 70af0a7..04b2ed2 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -139,6 +139,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 	u64 seq;
 	int i = 0;
 	int retval = 0;
+	bool delivery_failure;
 #ifdef CONFIG_NET
 	struct uevent_sock *ue_sk;
 #endif
@@ -251,6 +252,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 	if (retval)
 		goto exit;
 
+	delivery_failure = false;
 #if defined(CONFIG_NET)
 	/* send netlink message */
 	mutex_lock(&uevent_sock_mutex);
@@ -281,14 +283,17 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 							    0, 1, GFP_KERNEL,
 							    kobj_bcast_filter,
 							    kobj);
-			/* ENOBUFS should be handled in userspace */
-			if (retval == -ENOBUFS)
+			if (retval == -ESRCH)
 				retval = 0;
+			else if (retval)
+				delivery_failure = true;
 		} else
-			retval = -ENOMEM;
+			delivery_failure = true;
 	}
 	mutex_unlock(&uevent_sock_mutex);
 #endif
+	if (delivery_failure)
+		retval = -ENOBUFS;
 
 	/* call uevent_helper, usually only enabled during early boot */
 	if (uevent_helper[0] && !kobj_usermode_filter(kobj)) {


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