2020-03-20 23:47:29

by Michal Kubecek

Subject: [PATCH net v2] netlink: check for null extack in cookie helpers

Unlike NL_SET_ERR_* macros, nl_set_extack_cookie_u64() and
nl_set_extack_cookie_u32() helpers do not check extack argument for null
and neither do their callers, as syzbot recently discovered for
ethnl_parse_header().

Instead of fixing the callers and leaving the trap in place, add check of
null extack to both helpers to make them consistent with NL_SET_ERR_*
macros.

v2: drop incorrect second Fixes tag

Fixes: 2363d73a2f3e ("ethtool: reject unrecognized request flags")
Reported-by: [email protected]
Signed-off-by: Michal Kubecek <[email protected]>
---
include/linux/netlink.h | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 4090524c3462..60739d0cbf93 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -115,6 +115,8 @@ static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
{
u64 __cookie = cookie;

+ if (!extack)
+ return;
memcpy(extack->cookie, &__cookie, sizeof(__cookie));
extack->cookie_len = sizeof(__cookie);
}
@@ -124,6 +126,8 @@ static inline void nl_set_extack_cookie_u32(struct netlink_ext_ack *extack,
{
u32 __cookie = cookie;

+ if (!extack)
+ return;
memcpy(extack->cookie, &__cookie, sizeof(__cookie));
extack->cookie_len = sizeof(__cookie);
}
--
2.25.1

2020-03-24 04:21:54

by David Miller

Subject: Re: [PATCH net v2] netlink: check for null extack in cookie helpers

From: Michal Kubecek <[email protected]>
Date: Sat, 21 Mar 2020 00:46:50 +0100 (CET)

> Unlike NL_SET_ERR_* macros, nl_set_extack_cookie_u64() and
> nl_set_extack_cookie_u32() helpers do not check extack argument for null
> and neither do their callers, as syzbot recently discovered for
> ethnl_parse_header().
>
> Instead of fixing the callers and leaving the trap in place, add check of
> null extack to both helpers to make them consistent with NL_SET_ERR_*
> macros.
>
> v2: drop incorrect second Fixes tag
>
> Fixes: 2363d73a2f3e ("ethtool: reject unrecognized request flags")
> Reported-by: [email protected]
> Signed-off-by: Michal Kubecek <[email protected]>

Applied, thanks Michal.