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; } return ret; }
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!
From: Pablo Neira Ayuso [mailto:pablo@netfilter.org] On Mon, Dec 11, 2017 at 06:30:24PM -0500, Debabrata Banerjee wrote:
- } 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.
Many ways to fix it, but I thought including the comment was appropriate. Happy to change it if we want simpler instead.
-Deb
On Tue, Dec 12, 2017 at 12:36:35AM +0000, Banerjee, Debabrata wrote:
From: Pablo Neira Ayuso [mailto:pablo@netfilter.org] On Mon, Dec 11, 2017 at 06:30:24PM -0500, Debabrata Banerjee wrote:
- } 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.
Many ways to fix it, but I thought including the comment was appropriate. Happy to change it if we want simpler instead.
OK, let's take this one.
Please, send a patch in git-format-patch, that we can pass to -stable.
Cc netfilter-devel@vger.kernel.org and stable@vger.kernel.org should be fine, you can also include gregkh@linuxfoundation.org since he maintains 4.9-stable.
I'll ack this by when you send it.
Thanks!
linux-stable-mirror@lists.linaro.org
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Banerjee, Debabrata -
Debabrata Banerjee
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Pablo Neira Ayuso