When sockets are added to a sockmap or sockhash we allocate and init a
psock. Then update the proto ops with sock_map_init_proto the flow is
sock_hash_update_common
sock_map_link
psock = sock_map_psock_get_checked() <-returns existing psock
sock_map_init_proto(sk, psock) <- updates sk_proto
If the socket is already in a map this results in the sock_map_init_proto
being called multiple times on the same socket. We do this because when
a socket is added to multiple maps this might result in a new set of BPF
programs being attached to the socket requiring an updated ops struct.
This creates a rule where it must be safe to call psock_update_sk_prot
multiple times. When we added a fix for UAF through unix sockets in patch
4dd9a38a753fc we broke this rule by adding a sock_hold in that path
to ensure the sock is not released. The result is if a af_unix stream sock
is placed in multiple maps it results in a memory leak because we call
sock_hold multiple times with only a single sock_put on it.
Fixes: 8866730aed ("bpf, sockmap: af_unix stream sockets need to hold ref for pair sock")
Reported-by: Xingwei Lee <xrivendell7@gmail.com>
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20231221232327.43678-2-john.fastabend@gmail.com
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