[Linux-kernel-mentees] [PATCH net] ethtool: strset: Fix out of bound read in strset_parse_request()
From: Anmol Karn
Date: Sat Oct 10 2020 - 19:02:34 EST
Flag ``ETHTOOL_A_STRSET_COUNTS_ONLY`` tells the kernel to only return the string
counts of the sets, but, when req_info->counts_only tries to read the
tb[ETHTOOL_A_STRSET_COUNTS_ONLY] it gets out of bound.
- net/ethtool/strset.c
The bug seems to trigger in this line:
req_info->counts_only = tb[ETHTOOL_A_STRSET_COUNTS_ONLY];
Fix it by NULL checking for req_info->counts_only while
reading from tb[ETHTOOL_A_STRSET_COUNTS_ONLY].
Reported-by: syzbot+9d1389df89299fa368dc@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=730deff8fe9954a5e317924d9acff98d9c64a770
Signed-off-by: Anmol Karn <anmol.karan123@xxxxxxxxx>
---
When I tried to reduce the index of tb[] by 1, the crash reproducer was not working anymore,
hence it's probably reading from tb[ETHTOOL_A_STRSET_STRINGSETS], but this won't give the
strset 'count' and hence is not a plausible fix. But checking for the req_info->counts_only
seems legit.
If I have missed something please let me know, and I will work towards fixing it in next version.
net/ethtool/strset.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/ethtool/strset.c b/net/ethtool/strset.c
index 82707b662fe4..20a7b36698f3 100644
--- a/net/ethtool/strset.c
+++ b/net/ethtool/strset.c
@@ -174,7 +174,8 @@ static int strset_parse_request(struct ethnl_req_info *req_base,
if (ret < 0)
return ret;
- req_info->counts_only = tb[ETHTOOL_A_STRSET_COUNTS_ONLY];
+ if (req_info->counts_only)
+ req_info->counts_only = tb[ETHTOOL_A_STRSET_COUNTS_ONLY];
nla_for_each_nested(attr, nest, rem) {
u32 id;
--
2.28.0