[PATCH 3.2 192/221] gen_stats.c: Duplicate xstats buffer for later use

Ben Hutchings
2015-05-05T02:19:09Z

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

[ 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@gmail.com: remove a useless kfree()]

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/core/gen_stats.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

--- a/net/core/gen_stats.c
+++ b/net/core/gen_stats.c
@@ -31,6 +31,9 @@ gnet_stats_copy(struct gnet_dump *d, int
return 0;

nla_put_failure:
+ kfree(d->xstats);
+ d->xstats = NULL;
+ d->xstats_len = 0;
spin_unlock_bh(d->lock);
return -1;
}
@@ -204,7 +207,9 @@ 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;
}

@@ -212,6 +217,11 @@ gnet_stats_copy_app(struct gnet_dump *d,
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);

@@ -244,6 +254,9 @@ gnet_stats_finish_copy(struct gnet_dump
return -1;
}

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