[Bridge] [PATCH net] bridge: netfilter stp fix reference to uninitialized data

[Stephen Hemminger]

The destination mac (destmac) is only valid if EBT_DESTMAC flag
is set. Fix by changing the order of the comparison to look for
the flag first.

Reported-by: syzbot+***@syzkaller.appspotmail.com
Signed-off-by: Stephen Hemminger <***@networkplumber.org>
---
Note: no fixes since this bug goes back to pre-git days.
Should go to stable as well.

net/bridge/netfilter/ebt_stp.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/bridge/netfilter/ebt_stp.c b/net/bridge/netfilter/ebt_stp.c
index 47ba98db145d..46c1fe7637ea 100644
--- a/net/bridge/netfilter/ebt_stp.c
+++ b/net/bridge/netfilter/ebt_stp.c
@@ -161,8 +161,8 @@ static int ebt_stp_mt_check(const struct xt_mtchk_param *par)
/* Make sure the match only receives stp frames */
if (!par->nft_compat &&
(!ether_addr_equal(e->destmac, eth_stp_addr) ||
- !is_broadcast_ether_addr(e->destmsk) ||
- !(e->bitmask & EBT_DESTMAC)))
+ !(e->bitmask & EBT_DESTMAC) ||
+ !is_broadcast_ether_addr(e->destmsk)))
return -EINVAL;

return 0;