netfilter: ebtables: fix compat entry padding

On arm64, ebt_entry_{match,watcher,target} structs are 40 bytes long
while on 32-bit arm these structs have a size of 36 bytes.

COMPAT_XT_ALIGN() macro cannot be used here to determine the necessary
padding for the CONFIG_COMPAT because it imposes an 8-byte boundary
alignment, condition that is not found in 32-bit ebtables application.

Signed-off-by: Alin Nastac <alin.nastac@gmail.com>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 6ba639f6c51d12446e385af1b688fee0e46e884e..5f459c8b7937652f90434872c4e6879225b32ae8 100644 (file)
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1610,16 +1610,16 @@ struct compat_ebt_entry_mwt {
                compat_uptr_t ptr;
        } u;
        compat_uint_t match_size;
-       compat_uint_t data[0];
+       compat_uint_t data[0] __attribute__ ((aligned (__alignof__(struct compat_ebt_replace))));
 };
 
 /* account for possible padding between match_size and ->data */
 static int ebt_compat_entry_padsize(void)
 {
-       BUILD_BUG_ON(XT_ALIGN(sizeof(struct ebt_entry_match)) <
-                       COMPAT_XT_ALIGN(sizeof(struct compat_ebt_entry_mwt)));
-       return (int) XT_ALIGN(sizeof(struct ebt_entry_match)) -
-                       COMPAT_XT_ALIGN(sizeof(struct compat_ebt_entry_mwt));
+       BUILD_BUG_ON(sizeof(struct ebt_entry_match) <
+                       sizeof(struct compat_ebt_entry_mwt));
+       return (int) sizeof(struct ebt_entry_match) -
+                       sizeof(struct compat_ebt_entry_mwt);
 }
 
 static int ebt_compat_match_offset(const struct xt_match *match,