After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by
tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When
close the sock, tls_sk_proto_close() is called for sock->sk_prot->close
is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later
in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly
occurred. That will trigger the following bug.

=================================================================
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
RIP: 0010:tls_sk_proto_close+0xd8/0xaf0 net/tls/tls_main.c:306
Call Trace:
 <TASK>
 tls_sk_proto_close+0x356/0xaf0 net/tls/tls_main.c:329
 inet_release+0x12e/0x280 net/ipv4/af_inet.c:428
 __sock_release+0xcd/0x280 net/socket.c:650
 sock_close+0x18/0x20 net/socket.c:1365

Updating a proto which is same with sock->sk_prot is incorrect. Add proto
and sock->sk_prot equality check at the head of tls_update() to fix it.

Fixes: 95fa145479fb ("bpf: sockmap/tls, close can race with map free")
Reported-by: syzbot+29c3c12f3214b85ad081@syzkaller.appspotmail.com
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
---
 net/tls/tls_main.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index da176411c1b5..46bd5f26338b 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -921,6 +921,9 @@ static void tls_update(struct sock *sk, struct proto *p,
 {
 	struct tls_context *ctx;
 
+	if (sk->sk_prot == p)
+		return;
+
 	ctx = tls_get_ctx(sk);
 	if (likely(ctx)) {
 		ctx->sk_write_space = write_space;
-- 
2.25.1

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Mon, 20 Jun 2022 12:35:08 +0800 you wrote:
> After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by
> tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When
> close the sock, tls_sk_proto_close() is called for sock->sk_prot->close
> is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later
> in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly
> occurred. That will trigger the following bug.
> 
> [...]

Here is the summary with links:
  - [net] net/tls: fix tls_sk_proto_close executed repeatedly
    https://git.kernel.org/netdev/net/c/69135c572d1f

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

On Mon, 20 Jun 2022 09:20:12 +0000 patchwork-bot+netdevbpf@kernel.org
wrote:
> On Mon, 20 Jun 2022 12:35:08 +0800 you wrote:
> > After setting the sock ktls, update ctx->sk_proto to sock->sk_prot by
> > tls_update(), so now ctx->sk_proto->close is tls_sk_proto_close(). When
> > close the sock, tls_sk_proto_close() is called for sock->sk_prot->close
> > is tls_sk_proto_close(). But ctx->sk_proto->close() will be executed later
> > in tls_sk_proto_close(). Thus tls_sk_proto_close() executed repeatedly
> > occurred. That will trigger the following bug.
> > 
> > [...]  
> 
> Here is the summary with links:
>   - [net] net/tls: fix tls_sk_proto_close executed repeatedly
>     https://git.kernel.org/netdev/net/c/69135c572d1f

No, this is not the right fix. The AF_UNIX restructuring has moved the
ULP check too late. I'll send a revert and the correct fix.