tcp: fix potential double free issue for fastopen_req
tp->fastopen_req could potentially be double freed if a malicious user does the following: 1. Enable TCP_FASTOPEN_CONNECT sockopt and do a connect() on the socket. 2. Call connect() with AF_UNSPEC to disconnect the socket. 3. Make this socket a listening socket by calling listen(). 4. Accept incoming connections and generate child sockets. All child sockets will get a copy of the pointer of fastopen_req. 5. Call close() on all sockets. fastopen_req will get freed multiple times. Fixes: 19f6d3f3 ("net/tcp-fastopen: Add new API support") Reported-by: Andrey Konovalov <andreyknvl@google.com> Signed-off-by: Wei Wang <weiwan@google.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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