[PATCH net] ethtool: fix string set id check

[Michal Kubecek]

Syzbot reported a shift of a u32 by more than 31 in strset_parse_request()
which is undefined behavior. This is caused by range check of string set id
using variable ret (which is always 0 at this point) instead of id (string
set id from request).

Fixes: 71921690f974 ("ethtool: provide string sets with STRSET_GET request")
Reported-by: syzbot+96523fb438937cd01...@syzkaller.appspotmail.com
Signed-off-by: Michal Kubecek <mkube...@suse.cz>
---
 net/ethtool/strset.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c
index 0baad0ce1832..c3a5489964cd 100644
--- a/net/ethtool/strset.c
+++ b/net/ethtool/strset.c
@@ -182,7 +182,7 @@ static int strset_parse_request(struct ethnl_req_info 
*req_base,
                ret = strset_get_id(attr, &id, extack);
                if (ret < 0)
                        return ret;
-               if (ret >= ETH_SS_COUNT) {
+               if (id >= ETH_SS_COUNT) {
                        NL_SET_ERR_MSG_ATTR(extack, attr,
                                            "unknown string set id");
                        return -EOPNOTSUPP;
-- 
2.29.2