Hi,
Thanks for catching up this, see below.
On Mon, Dec 11, 2017 at 06:30:24PM -0500, Debabrata Banerjee wrote:
A verdict of NF_STOLEN after NF_QUEUE will cause an incorrect return value and a potential kernel panic via double free of skb's
This was broken by commit 7034b566a4e7 ("netfilter: fix nf_queue handling") and subsequently fixed in v4.10 by commit c63cbc460419 ("netfilter: use switch() to handle verdict cases from nf_hook_slow()"). However that commit cannot be cleanly cherry-picked to v4.9
Signed-off-by: Debabrata Banerjee dbanerje@akamai.com
This fix is only needed for v4.9 stable since v4.10+ does not have the issue
net/netfilter/core.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/net/netfilter/core.c b/net/netfilter/core.c index 004af030ef1a..d869ea50623e 100644 --- a/net/netfilter/core.c +++ b/net/netfilter/core.c @@ -364,6 +364,11 @@ int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state) ret = nf_queue(skb, state, &entry, verdict); if (ret == 1 && entry) goto next_hook;
- } else {
/* Implicit handling for NF_STOLEN, as well as any other* non conventional verdicts.*/ret = 0;
Another possibility (more simple?) would be this:
int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state) { struct nf_hook_entry *entry; unsigned int verdict; - int ret = 0; + int ret;
entry = rcu_dereference(state->hook_entries); next_hook: + ret = 0;
Basically, make sure ret is set to zero when jumping to the next_hook label.
Thanks!