Re: [PATCH net v10] skb_expand_head() adjust skb->truesize incorrectly

On 10/22/21 3:28 AM, Vasily Averin wrote:

Christoph Paasch reports [1] about incorrect skb->truesize
after skb_expand_head() call in ip6_xmit.
This may happen because of two reasons:
- skb_set_owner_w() for newly cloned skb is called too early,
before pskb_expand_head() where truesize is adjusted for (!skb-sk) case.
- pskb_expand_head() does not adjust truesize in (skb->sk) case.
In this case sk->sk_wmem_alloc should be adjusted too.

[1] https://lkml.org/lkml/2021/8/20/1082

Fixes: f1260ff15a71 ("skbuff: introduce skb_expand_head()")
Fixes: 2d85a1b31dde ("ipv6: ip6_finish_output2: set sk into newly allocated nskb")
Reported-by: Christoph Paasch <redacted>
Signed-off-by: Vasily Averin <redacted>
---
v10: is_skb_wmem() was moved into separate header (it depends on net/tcp.h)
     use it after pskb_expand_head() insted of strange sock_edemux check

SGTM, thanks !

Reviewed-by: Eric Dumazet <edumazet@google.com>