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Subject[PATCH] netfilter: fix stringop-overflow warning with UBSAN
Date
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
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