From cfc56f85e72f5b9c5c5be26dc2b16518d36a7868 Mon Sep 17 00:00:00 2001 From: Antoine Tenart Date: Mon, 7 Feb 2022 18:13:18 +0100 Subject: [PATCH 1/2] net: do not keep the dst cache when uncloning an skb dst and its metadata 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 Reported-by: Vlad Buslov Tested-by: Vlad Buslov Signed-off-by: Antoine Tenart Acked-by: Paolo Abeni Signed-off-by: David S. Miller --- 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 14efa0ded75d..b997e0c1e362 100644 --- a/include/net/dst_metadata.h +++ b/include/net/dst_metadata.h @@ -123,6 +123,19 @@ 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); From 9eeabdf17fa0ab75381045c867c370f4cc75a613 Mon Sep 17 00:00:00 2001 From: Antoine Tenart Date: Mon, 7 Feb 2022 18:13:19 +0100 Subject: [PATCH 2/2] net: fix a memleak when uncloning an skb dst and its metadata When uncloning an skb dst and its associated metadata, a new dst+metadata is allocated and later replaces the old one in the skb. This is helpful to have a non-shared dst+metadata attached to a specific skb. The issue is the uncloned dst+metadata is initialized with a refcount of 1, which is increased to 2 before attaching it to the skb. When tun_dst_unclone returns, the dst+metadata is only referenced from a single place (the skb) while its refcount is 2. Its refcount will never drop to 0 (when the skb is consumed), leading to a memory leak. Fix this by removing the call to dst_hold in tun_dst_unclone, as the dst+metadata refcount is already 1. Fixes: fc4099f17240 ("openvswitch: Fix egress tunnel info.") Cc: Pravin B Shelar Reported-by: Vlad Buslov Tested-by: Vlad Buslov Signed-off-by: Antoine Tenart Signed-off-by: David S. Miller --- include/net/dst_metadata.h | 1 - 1 file changed, 1 deletion(-) diff --git a/include/net/dst_metadata.h b/include/net/dst_metadata.h index b997e0c1e362..adab27ba1ecb 100644 --- a/include/net/dst_metadata.h +++ b/include/net/dst_metadata.h @@ -137,7 +137,6 @@ static inline struct metadata_dst *tun_dst_unclone(struct sk_buff *skb) #endif skb_dst_drop(skb); - dst_hold(&new_md->dst); skb_dst_set(skb, &new_md->dst); return new_md; }