Re: [PATCH][next] xfrm: Add error handling when nla_put_u32() returns an error

From: Przemek Kitszel
Date: Wed Nov 13 2024 - 09:12:31 EST


On 11/13/24 00:36, Everest K.C. wrote:
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@xxxxxxxxxxxxxxxx>
---
net/xfrm/xfrm_user.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index f0ee0c7a59dd..a784598cc7cf 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -2607,9 +2607,12 @@ 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);
if (err)

this is a fix indeed,
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
--
I find nla_put*() familiy error handling very ugly for the calling code,
especially given that some of the calls are conditional

I would like to refactor it some day, to give the caller possibility to
just put all the needed fields and check the error once at the end.
Nesting complicates things a bit, but perhaps it could be also covered
in such way (didn't checked yet).