netdev - [PATCH net 1/2] gen_stats.c: Duplicate xstats buffer for later use

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Message-ID: <20150108103518.GA7214@zenon.in.qult.net>
Date:	Thu, 8 Jan 2015 11:35:18 +0100
From:	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>
To:	netdev@...r.kernel.org
Subject: [PATCH net 1/2] gen_stats.c: Duplicate xstats buffer for later use

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.

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>
---
 net/core/gen_stats.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/net/core/gen_stats.c b/net/core/gen_stats.c
index 0c08062..5770a0e 100644
--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -305,7 +305,10 @@ int
 gnet_stats_copy_app(struct gnet_dump *d, void *st, int len)
 {
 	if (d->compat_xstats) {
-		d->xstats = st;
+		d->xstats = kmalloc(len, GFP_KERNEL);
+		if (!d->xstats)
+			goto kmalloc_failure;
+		memcpy(d->xstats, st, len);
 		d->xstats_len = len;
 	}
 
@@ -313,6 +316,9 @@ gnet_stats_copy_app(struct gnet_dump *d, void *st, int len)
 		return gnet_stats_copy(d, TCA_STATS_APP, st, len);
 
 	return 0;
+kmalloc_failure:
+	spin_unlock_bh(d->lock);
+	return -1;
 }
 EXPORT_SYMBOL(gnet_stats_copy_app);
 
@@ -340,8 +346,13 @@ gnet_stats_finish_copy(struct gnet_dump *d)
 			return -1;
 
 	if (d->compat_xstats && d->xstats) {
-		if (gnet_stats_copy(d, d->compat_xstats, d->xstats,
-			d->xstats_len) < 0)
+		int	result = gnet_stats_copy(d, d->compat_xstats,
+						 d->xstats, d->xstats_len);
+		kfree(d->xstats);
+		d->xstats = NULL;
+		d->xstats_len = 0;
+
+		if (result < 0)
 			return -1;
 	}
 
-- 
1.9.1
--
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