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author | Dae R. Jeong <threeearcat@gmail.com> | 2024-05-21 13:34:38 +0300 |
---|---|---|
committer | Paolo Abeni <pabeni@redhat.com> | 2024-05-23 13:03:26 +0300 |
commit | 91e61dd7a0af660408e87372d8330ceb218be302 (patch) | |
tree | 69bc4696c019ef04ef22c34400827fd86e7ffbbe /net/tls | |
parent | 3b1c92f8e5371700fada307cc8fd2c51fa7bc8c1 (diff) | |
download | linux-91e61dd7a0af660408e87372d8330ceb218be302.tar.xz |
tls: fix missing memory barrier in tls_init
In tls_init(), a write memory barrier is missing, and store-store
reordering may cause NULL dereference in tls_{setsockopt,getsockopt}.
CPU0 CPU1
----- -----
// In tls_init()
// In tls_ctx_create()
ctx = kzalloc()
ctx->sk_proto = READ_ONCE(sk->sk_prot) -(1)
// In update_sk_prot()
WRITE_ONCE(sk->sk_prot, tls_prots) -(2)
// In sock_common_setsockopt()
READ_ONCE(sk->sk_prot)->setsockopt()
// In tls_{setsockopt,getsockopt}()
ctx->sk_proto->setsockopt() -(3)
In the above scenario, when (1) and (2) are reordered, (3) can observe
the NULL value of ctx->sk_proto, causing NULL dereference.
To fix it, we rely on rcu_assign_pointer() which implies the release
barrier semantic. By moving rcu_assign_pointer() after ctx->sk_proto is
initialized, we can ensure that ctx->sk_proto are visible when
changing sk->sk_prot.
Fixes: d5bee7374b68 ("net/tls: Annotate access to sk_prot with READ_ONCE/WRITE_ONCE")
Signed-off-by: Yewon Choi <woni9911@gmail.com>
Signed-off-by: Dae R. Jeong <threeearcat@gmail.com>
Link: https://lore.kernel.org/netdev/ZU4OJG56g2V9z_H7@dragonet/T/
Link: https://lore.kernel.org/r/Zkx4vjSFp0mfpjQ2@libra05
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/tls')
-rw-r--r-- | net/tls/tls_main.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c index b4674f03d71a..90b7f253d363 100644 --- a/net/tls/tls_main.c +++ b/net/tls/tls_main.c @@ -816,9 +816,17 @@ struct tls_context *tls_ctx_create(struct sock *sk) return NULL; mutex_init(&ctx->tx_lock); - rcu_assign_pointer(icsk->icsk_ulp_data, ctx); ctx->sk_proto = READ_ONCE(sk->sk_prot); ctx->sk = sk; + /* Release semantic of rcu_assign_pointer() ensures that + * ctx->sk_proto is visible before changing sk->sk_prot in + * update_sk_prot(), and prevents reading uninitialized value in + * tls_{getsockopt, setsockopt}. Note that we do not need a + * read barrier in tls_{getsockopt,setsockopt} as there is an + * address dependency between sk->sk_proto->{getsockopt,setsockopt} + * and ctx->sk_proto. + */ + rcu_assign_pointer(icsk->icsk_ulp_data, ctx); return ctx; } |