[prev in list] [next in list] [prev in thread] [next in thread] 

List:       netfilter-devel
Subject:    [PATCH] netfilter: fix stringop-overflow warning with UBSAN
From:       Arnd Bergmann <arnd () arndb ! de>
Date:       2017-07-31 10:09:03
Message-ID: 20170731100913.465530-1-arnd () arndb ! de
[Download RAW message or body]

Using gcc-7 with UBSAN enabled, we get this false-positive warning:

net/netfilter/ipset/ip_set_core.c: In function 'ip_set_sockfn_get':
net/netfilter/ipset/ip_set_core.c:1998:3: error: 'strncpy' writing 32 bytes into a \
region of size 2 overflows the destination [-Werror=stringop-overflow=]  \
strncpy(req_get->set.name, set ? set->name : "",  \
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  sizeof(req_get->set.name));
    ~~~~~~~~~~~~~~~~~~~~~~~~~~

This seems completely bogus, and I could not find a nice workaround.
To work around it in a less elegant way, I change the ?: operator
into an if()/else() construct.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 net/netfilter/ipset/ip_set_core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
index e495b5e484b1..d7ebb021003b 100644
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -1995,8 +1995,12 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user \
*user, int *len)  }
 		nfnl_lock(NFNL_SUBSYS_IPSET);
 		set = ip_set(inst, req_get->set.index);
-		strncpy(req_get->set.name, set ? set->name : "",
-			IPSET_MAXNAMELEN);
+		if (set)
+			strncpy(req_get->set.name, set->name,
+				sizeof(req_get->set.name));
+		else
+			memset(req_get->set.name, '\0',
+			       sizeof(req_get->set.name));
 		nfnl_unlock(NFNL_SUBSYS_IPSET);
 		goto copy;
 	}
-- 
2.9.0

--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html


[prev in list] [next in list] [prev in thread] [next in thread]