[PATCH 6.9 4/5] keys: Fix overwrite of key expiration on instantiation

6.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Silvio Gissi <redacted>

commit 9da27fb65a14c18efd4473e2e82b76b53ba60252 upstream.

The expiry time of a key is unconditionally overwritten during
instantiation, defaulting to turn it permanent. This causes a problem
for DNS resolution as the expiration set by user-space is overwritten to
TIME64_MAX, disabling further DNS updates. Fix this by restoring the
condition that key_set_expiry is only called when the pre-parser sets a
specific expiry.

Fixes: 39299bdd2546 ("keys, dns: Allow key types (eg. DNS) to be reclaimed immediately on expiry")
Signed-off-by: Silvio Gissi <redacted>
cc: David Howells <dhowells@redhat.com>
cc: Hazem Mohamed Abuelfotoh <redacted>
cc: linux-afs@lists.infradead.org
cc: linux-cifs@vger.kernel.org
cc: keyrings@vger.kernel.org
cc: netdev@vger.kernel.org
cc: stable@vger.kernel.org
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 security/keys/key.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/security/keys/key.c
+++ b/security/keys/key.c

@@ -463,7 +463,8 @@ static int __key_instantiate_and_link(st
 			if (authkey)
 				key_invalidate(authkey);
 
-			key_set_expiry(key, prep->expiry);
+			if (prep->expiry != TIME64_MAX)
+				key_set_expiry(key, prep->expiry);
 		}
 	}