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mptcp: check the protocol in tcp_sk() with DEBUG_NET

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Fuzzers and static checkers might not detect when tcp_sk() is used with
a non tcp_sock structure.

This kind of mistake already happened a few times with MPTCP: when
wrongly using TCP-specific helpers with mptcp_sock pointers. On the
other hand, there are many 'tcp_xxx()' helpers that are taking a 'struct
sock' pointer as arguments, and some of them are only looking at fields
from 'struct sock', and nothing from 'struct tcp_sock'. It is then
tempting to use them with a 'struct mptcp_sock'.

So a new simple check is done when CONFIG_DEBUG_NET is enabled to tell
kernel devs when a non-TCP socket is being used as a TCP one. 'tcp_sk()'
macro is then re-defined to add a WARN when an unexpected socket is
being used.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240223-upstream-net-next-20240223-misc-improvements-v1-3-b6c8a10396bd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Matthieu Baerts (NGI0) 2024-02-23 21:17:55 +01:00 committed by Jakub Kicinski
parent 28de50eeb7
commit dcc03f270d
1 changed files with 10 additions and 0 deletions
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10
net/mptcp/protocol.h
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@ -348,6 +348,16 @@ static inline void msk_owned_by_me(const struct mptcp_sock *msk)
sock_owned_by_me((const struct sock *)msk);
}
#ifdef CONFIG_DEBUG_NET
/* MPTCP-specific: we might (indirectly) call this helper with the wrong sk */
#undef tcp_sk
#define tcp_sk(ptr) ({ \
typeof(ptr) _ptr = (ptr); \
WARN_ON(_ptr->sk_protocol != IPPROTO_TCP); \
container_of_const(_ptr, struct tcp_sock, inet_conn.icsk_inet.sk); \
})
#endif
#define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
/* the msk socket don't use the backlog, also account for the bulk