[3.16.y-ckt stable] Patch "gen_stats.c: Duplicate xstats buffer for later use" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    gen_stats.c: Duplicate xstats buffer for later use

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From e2bc1237a9356ba001d3e3a95c5af54670b51cb6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ignacy=20Gaw=C4=99dzki?=
 <ignacy.gawedzki at green-communications.fr>
Date: Fri, 13 Feb 2015 14:47:05 -0800
Subject: gen_stats.c: Duplicate xstats buffer for later use
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit 1c4cff0cf55011792125b6041bc4e9713e46240f upstream.

The gnet_stats_copy_app() function gets called, more often than not, with its
second argument a pointer to an automatic variable in the caller's stack.
Therefore, to avoid copying garbage afterwards when calling
gnet_stats_finish_copy(), this data is better copied to a dynamically allocated
memory that gets freed after use.

[xiyou.wangcong at gmail.com: remove a useless kfree()]

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki at green-communications.fr>
Signed-off-by: Cong Wang <xiyou.wangcong at gmail.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/core/gen_stats.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index 9d3d9e78397b..372ac662adf9 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -32,6 +32,9 @@ gnet_stats_copy(struct gnet_dump *d, int type, void *buf, int size)
 	return 0;

 nla_put_failure:
+	kfree(d->xstats);
+	d->xstats = NULL;
+	d->xstats_len = 0;
 	spin_unlock_bh(d->lock);
 	return -1;
 }
@@ -217,7 +220,9 @@ int
 gnet_stats_copy_app(struct gnet_dump *d, void *st, int len)
 {
 	if (d->compat_xstats) {
-		d->xstats = st;
+		d->xstats = kmemdup(st, len, GFP_ATOMIC);
+		if (!d->xstats)
+			goto err_out;
 		d->xstats_len = len;
 	}

@@ -225,6 +230,11 @@ gnet_stats_copy_app(struct gnet_dump *d, void *st, int len)
 		return gnet_stats_copy(d, TCA_STATS_APP, st, len);

 	return 0;
+
+err_out:
+	d->xstats_len = 0;
+	spin_unlock_bh(d->lock);
+	return -1;
 }
 EXPORT_SYMBOL(gnet_stats_copy_app);

@@ -257,6 +267,9 @@ gnet_stats_finish_copy(struct gnet_dump *d)
 			return -1;
 	}

+	kfree(d->xstats);
+	d->xstats = NULL;
+	d->xstats_len = 0;
 	spin_unlock_bh(d->lock);
 	return 0;
 }