[patch 42/50] ebtables: dont compute gap before checking struct type

[Chris Wright]

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

From: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>

We cannot compute the gap until we know we have a 'struct ebt_entry'
and not 'struct ebt_entries'.  Failure to check can cause crash.

Tested-by: Santiago Garcia Mantinan <manty@xxxxxxxxx>
Acked-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Acked-by: Patrick McHardy <kaber@xxxxxxxxx>
Signed-off-by: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx>
Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
---
 net/bridge/netfilter/ebtables.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- linux-2.6.19.1.orig/net/bridge/netfilter/ebtables.c
+++ linux-2.6.19.1/net/bridge/netfilter/ebtables.c
@@ -575,7 +575,7 @@ ebt_check_entry(struct ebt_entry *e, str
 	struct ebt_entry_target *t;
 	struct ebt_target *target;
 	unsigned int i, j, hook = 0, hookmask = 0;
-	size_t gap = e->next_offset - e->target_offset;
+	size_t gap;
 	int ret;
 
 	/* don't mess with the struct ebt_entries */
@@ -625,6 +625,7 @@ ebt_check_entry(struct ebt_entry *e, str
 	if (ret != 0)
 		goto cleanup_watchers;
 	t = (struct ebt_entry_target *)(((char *)e) + e->target_offset);
+	gap = e->next_offset - e->target_offset;
 	target = find_target_lock(t->u.name, &ret, &ebt_mutex);
 	if (!target)
 		goto cleanup_watchers;

--
-
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