xfrm: Add error handling when nla_put_u32() returns an error

BugLink: https://bugs.launchpad.net/bugs/2103829

commit 9d287e70c51f1c141ac588add261ed2efdd6fc6b upstream.

Error handling is missing when call to nla_put_u32() fails.
Handle the error when the call to nla_put_u32() returns an error.

The error was reported by Coverity Scan.
Report:
CID 1601525: (#1 of 1): Unused value (UNUSED_VALUE)
returned_value: Assigning value from nla_put_u32(skb, XFRMA_SA_PCPU, x->pcpu_num)
to err here, but that stored value is overwritten before it can be used

Fixes: 1ddf9916ac09 ("xfrm: Add support for per cpu xfrm state handling.")
Signed-off-by: Everest K.C. <everestkc@everestkc.com.np>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>
Signed-off-by: Mehmet Basaran <mehmet.basaran@canonical.com>

Author: everestkc

net/xfrm/xfrm_user.c

@@ -2609,8 +2609,11 @@ static int build_aevent(struct sk_buff *skb, struct xfrm_state *x, const struct
 	err = xfrm_if_id_put(skb, x->if_id);
 	if (err)
 		goto out_cancel;
-	if (x->pcpu_num != UINT_MAX)
+	if (x->pcpu_num != UINT_MAX) {
 		err = nla_put_u32(skb, XFRMA_SA_PCPU, x->pcpu_num);
+		if (err)
+			goto out_cancel;
+	}
 
 	if (x->dir) {
 		err = nla_put_u8(skb, XFRMA_SA_DIR, x->dir);