On Wed, 13 Nov 2024 18:46:39 +0000 Dmitry Safonov via B4 Relay wrote: > 2. Inet-diag allocates netlink message for sockets in > inet_diag_dump_one_icsk(), which uses a TCP-diag callback > .idiag_get_aux_size(), that pre-calculates the needed space for > TCP-diag related information. But as neither socket lock nor > rcu_readlock() are held between allocation and the actual TCP > info filling, the TCP-related space requirement may change before > reaching tcp_diag_put_md5sig(). I.e., the number of TCP-MD5 keys on > a socket. Thankfully, TCP-MD5-diag won't overwrite the skb, but will > return EMSGSIZE, triggering WARN_ON() in inet_diag_dump_one_icsk(). Hi Eric! This was posted while you were away -- any thoughts or recommendation on how to address the required nl message size changing? Or other problems pointed out by Dmitry? My suggestion in the subthread is to re-dump with a fixed, large buffer on EMSGSIZE, but that's not super clean..
