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@xxxxxxxxxx>
>
> ---
>
> 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!