| Message ID | 20170731100913.465530-1-arnd@arndb.de |
|---|---|
| State | New |
| Headers | show |
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@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, , > - 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 : ""; David
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; }
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(-) -- 2.9.0