4.17-stable review patch. If anyone has any objections, please let me know.
------------------ From: John Fastabend <[email protected]> [ Upstream commit 0c6bc6e531a6db36f49622f1f115770160f7afb0 ] Multiple BPF helpers in use by sk_skb programs calculate the max skb length using the __bpf_skb_max_len function. However, this calculates the max length using the skb->dev pointer which can be NULL when an sk_skb program is paired with an sk_msg program. To force this a sk_msg program needs to redirect into the ingress path of a sock with an attach sk_skb program. Then the the sk_skb program would need to call one of the helpers that adjust the skb size. To fix the null ptr dereference use SKB_MAX_ALLOC size if no dev is available. Fixes: 8934ce2fd081 ("bpf: sockmap redirect ingress support") Signed-off-by: John Fastabend <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- net/core/filter.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2516,7 +2516,8 @@ static int bpf_skb_net_shrink(struct sk_ static u32 __bpf_skb_max_len(const struct sk_buff *skb) { - return skb->dev->mtu + skb->dev->hard_header_len; + return skb->dev ? skb->dev->mtu + skb->dev->hard_header_len : + SKB_MAX_ALLOC; } static int bpf_skb_adjust_net(struct sk_buff *skb, s32 len_diff)
