linux-kernel - [PATCH 3.12 078/175] gen_stats.c: Duplicate xstats buffer for later use

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Message-Id: <85320d5deb74d8cdb05082a84ef8d13812c0ea9f.1426581621.git.jslaby@suse.cz>
Date:	Tue, 17 Mar 2015 09:40:56 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>,
	Cong Wang <xiyou.wangcong@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 078/175] gen_stats.c: Duplicate xstats buffer for later use

From: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit 1c4cff0cf55011792125b6041bc4e9713e46240f ]

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@...il.com: remove a useless kfree()]

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 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;
 }
-- 
2.3.0

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