[NETFILTER]: ip_tables: fix compat related crash

check_compat_entry_size_and_hooks iterates over the matches and calls
compat_check_calc_match, which loads the match and calculates the
compat offsets, but unlike the non-compat version, doesn't call
->checkentry yet. On error however it calls cleanup_matches, which in
turn calls ->destroy, which can result in crashes if the destroy
function (validly) expects to only get called after the checkentry
function.

Add a compat_release_match function that only drops the module reference
on error and rename compat_check_calc_match to compat_find_calc_match to
reflect the fact that it doesn't call the checkentry function.

Reported by Jan Engelhardt <jengelh@linux01.gwdg.de>

Signed-off-by: Dmitry Mishin <dim@openvz.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/include/linux/netfilter_ipv4/ip_tables.h b/include/linux/netfilter_ipv4/ip_tables.h
index 2f46dd728ee1..e992cd6b28f5 100644
--- a/include/linux/netfilter_ipv4/ip_tables.h
+++ b/include/linux/netfilter_ipv4/ip_tables.h
@@ -264,6 +264,26 @@ ipt_get_target(struct ipt_entry *e)
         __ret;                                                  \
 })
 
+/* fn returns 0 to continue iteration */
+#define IPT_ENTRY_ITERATE_CONTINUE(entries, size, n, fn, args...) \
+({                                                              \
+        unsigned int __i, __n;                                  \
+        int __ret = 0;                                          \
+        struct ipt_entry *__entry;                              \
+                                                                \
+        for (__i = 0, __n = 0; __i < (size);                    \
+             __i += __entry->next_offset, __n++) {              \
+                __entry = (void *)(entries) + __i;              \
+                if (__n < n)                                    \
+                        continue;                               \
+                                                                \
+                __ret = fn(__entry , ## args);                  \
+                if (__ret != 0)                                 \
+                        break;                                  \
+        }                                                       \
+        __ret;                                                  \
+})
+
 /*
  *      Main firewall chains definitions and global var's definitions.
  */