On 6/7/24 23:32, Kuniyuki Iwashima wrote:
From: Cong Wang <xiyou.wangcong@xxxxxxxxx>
Date: Fri, 7 Jun 2024 09:14:04 -0700
On Fri, Jun 07, 2024 at 01:27:47AM +0200, Florian Westphal wrote:
Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
Commit 219eee9c0d16 ("net: skbuff: add overflow debug check to pull/push
helpers") introduced an overflow debug check for pull/push helpers.
For __skb_pull() this makes sense because its callers rarely check its
return value. But for pskb_may_pull() it does not make sense, since its
return value is properly taken care of. Remove the one in
pskb_may_pull(), we can continue rely on its return value.
See 025f8ad20f2e3264d11683aa9cbbf0083eefbdcd which would not exist
without this check, I would not give up yet.
What's the point of that commit?
4b911a9690d7 would be better example. The warning actually found a
bug in NSH GSO.
Here's splats triggered by syzkaller using NSH over various tunnels.
https://lore.kernel.org/netdev/20240415222041.18537-2-kuniyu@xxxxxxxxxx/
Right. We discussed this before. I guess I forgot to send the fix.
Florian could you submit the suggestion I made before ?
diff --git a/net/core/filter.c b/net/core/filter.c
index
358870408a51e61f3cbc552736806e4dfee1ec39..da7aae6fd8ba557c66699d1cfebd47f18f442aa2
100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1662,6 +1662,11 @@ static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp);
static inline int __bpf_try_make_writable(struct sk_buff *skb,
unsigned int write_len)
{
+#if defined(CONFIG_DEBUG_NET)
+ /* Avoid a splat in pskb_may_pull_reason() */
+ if (write_len > INT_MAX)
+ return -EINVAL;
+#endif
return skb_ensure_writable(skb, write_len);
}
