Hi, [Sorry, at holiday I just cursory watched the mailing lists.] On Tue, 1 Aug 2017, David Laight wrote: > From: Arnd Bergmann > > Sent: 31 July 2017 11:09 > > 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@xxxxxxxx> > > --- > > 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, , > > - 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)); > > If you use strncpy() here, the compiler might optimise the code > back to 'how it was before'. > > Or, maybe an explicit temporary: 'const char *name = set ? set->name : ""; I think the best to go with the explicit temporary variable. The if-else construct is too much for such a case. Best regards, Jozsef - E-mail : kadlec@xxxxxxxxxxxxxxxxx, kadlecsik.jozsef@xxxxxxxxxxxxx PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences H-1525 Budapest 114, POB. 49, Hungary -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
