This is a note to let you know that I've just added the patch titled net: do not keep the dst cache when uncloning an skb dst and its metadata to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: net-do-not-keep-the-dst-cache-when-uncloning-an-skb-.patch and it can be found in the queue-4.9 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit ff0ce481d7afc00d984aed052b9360b4b30a40c8 Author: Antoine Tenart <atenart@xxxxxxxxxx> Date: Mon Feb 7 18:13:18 2022 +0100 net: do not keep the dst cache when uncloning an skb dst and its metadata [ 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@xxxxxxxxxx> Reported-by: Vlad Buslov <vladbu@xxxxxxxxxx> Tested-by: Vlad Buslov <vladbu@xxxxxxxxxx> Signed-off-by: Antoine Tenart <atenart@xxxxxxxxxx> Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h index 5a23535a5018d..33ca53057f318 100644 --- a/include/net/dst_metadata.h +++ b/include/net/dst_metadata.h @@ -97,6 +97,19 @@ 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);