[PATCH] net: tls: enable __GFP_ZERO upon tls_init()

Tetsuo Handa
2023-06-28T13:48:14Z

syzbot is reporting uninit-value at aes_encrypt(), for block cipher assumes
that bytes to encrypt/decrypt is multiple of block size for that cipher but
tls_alloc_encrypted_msg() is not initializing padding bytes when
required_size is not multiple of block cipher's block size.

In order to make sure that padding bytes are automatically initialized,
enable __GFP_ZERO flag when setsockopt(SOL_TCP, TCP_ULP, "tls") is called.

Reported-by: syzbot <syzbot+828dfc12440b4f6f305d@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=828dfc12440b4f6f305d
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
According to C reproducer, this problem happens when bpf_exec_tx_verdict() is
called with lower 4 bits of required_size being 0001 and does not happen when
being 0100. Thus, I assumed that this problem is caused by lack of initializing
padding bytes.
But I couldn't figure out why KMSAN reports this problem when bpf_exec_tx_verdict()
is called with lower 4 bits of required_size being 0001 for the second time and
does not report this problem when bpf_exec_tx_verdict() is called with lower
4 bits of required_size being 0001 for the first time. More deeper problem exists?
KMSAN reporting this problem when accessing u64 relevant?

net/tls/tls_main.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index f2e7302a4d96..cd5366966864 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -1025,6 +1025,7 @@ static int tls_init(struct sock *sk)
struct tls_context *ctx;
int rc = 0;

+ sk->sk_allocation |= __GFP_ZERO;
tls_build_proto(sk);

#ifdef CONFIG_TLS_TOE
--
2.34.1