From: Antoine Tenart atenart@kernel.org
[ Upstream commit cfc56f85e72f5b9c5c5be26dc2b16518d36a7868 ]
When uncloning an skb dst and its associated metadata a new dst+metadata is allocated and the tunnel information from the old metadata is copied over there.
The issue is the tunnel metadata has references to cached dst, which are copied along the way. When a dst+metadata refcount drops to 0 the metadata is freed including the cached dst entries. As they are also referenced in the initial dst+metadata, this ends up in UaFs.
In practice the above did not happen because of another issue, the dst+metadata was never freed because its refcount never dropped to 0 (this will be fixed in a subsequent patch).
Fix this by initializing the dst cache after copying the tunnel information from the old metadata to also unshare the dst cache.
Fixes: d71785ffc7e7 ("net: add dst_cache to ovs vxlan lwtunnel") Cc: Paolo Abeni pabeni@redhat.com Reported-by: Vlad Buslov vladbu@nvidia.com Tested-by: Vlad Buslov vladbu@nvidia.com Signed-off-by: Antoine Tenart atenart@kernel.org Acked-by: Paolo Abeni pabeni@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/dst_metadata.h | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h index 0b3c2aaed3c82..bf820c54e7ccd 100644 --- a/include/net/dst_metadata.h +++ b/include/net/dst_metadata.h @@ -121,6 +121,19 @@ static inline struct metadata_dst *tun_dst_unclone(struct sk_buff *skb)
memcpy(&new_md->u.tun_info, &md_dst->u.tun_info, sizeof(struct ip_tunnel_info) + md_size); +#ifdef CONFIG_DST_CACHE + /* Unclone the dst cache if there is one */ + if (new_md->u.tun_info.dst_cache.cache) { + int ret; + + ret = dst_cache_init(&new_md->u.tun_info.dst_cache, GFP_ATOMIC); + if (ret) { + metadata_dst_free(new_md); + return ERR_PTR(ret); + } + } +#endif + skb_dst_drop(skb); dst_hold(&new_md->dst); skb_dst_set(skb, &new_md->dst);