From: Dave Watson <davejwatson@fb.com>
Date: Thu, 12 Jul 2018 08:03:43 -0700
Subject: tls: Stricter error checking in zerocopy sendmsg path
Patch-mainline: v4.18-rc6
Git-commit: 32da12216e467dea70a09cd7094c30779ce0f9db
References: bsc#1109837

In the zerocopy sendmsg() path, there are error checks to revert
the zerocopy if we get any error code.  syzkaller has discovered
that tls_push_record can return -ECONNRESET, which is fatal, and
happens after the point at which it is safe to revert the iter,
as we've already passed the memory to do_tcp_sendpages.

Previously this code could return -ENOMEM and we would want to
revert the iter, but AFAIK this no longer returns ENOMEM after
a447da7d004 ("tls: fix waitall behavior in tls_sw_recvmsg"),
so we fail for all error codes.

Reported-by: syzbot+c226690f7b3126c5ee04@syzkaller.appspotmail.com
Reported-by: syzbot+709f2810a6a05f11d4d3@syzkaller.appspotmail.com
Signed-off-by: Dave Watson <davejwatson@fb.com>
Fixes: 3c4d7559159b ("tls: kernel TLS support")
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/tls/tls_sw.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -440,7 +440,7 @@ alloc_encrypted:
 			ret = tls_push_record(sk, msg->msg_flags, record_type);
 			if (!ret)
 				continue;
-			if (ret == -EAGAIN)
+			if (ret < 0)
 				goto send_end;
 
 			copied -= try_to_copy;