On Mon, 30 Nov 2015 18:55:23 -0600 ebiederm@xxxxxxxxxxxx (Eric W. Biederman) wrote:
> Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
>
> > On Mon, 30 Nov 2015 16:04:36 -0800 Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> >
> >> >> > +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS
> >> >> > + {
> >> >> > + .procname = "mmap_rnd_bits",
> >> >> > + .data = &mmap_rnd_bits,
> >> >> > + .maxlen = sizeof(mmap_rnd_bits),
> >> >> > + .mode = 0600,
> >> >> > + .proc_handler = proc_dointvec_minmax,
> >> >> > + .extra1 = (void *) &mmap_rnd_bits_min,
> >> >> > + .extra2 = (void *) &mmap_rnd_bits_max,
> >> >>
> >> >> hm, why the typecasts? They're unneeded and are omitted everywhere(?)
> >> >> else in kernel/sysctl.c.
> >> >
> >> > Oh. Casting away constness.
> >> >
> >> > What's the thinking here? They can change at any time so they aren't
> >> > const so we shouldn't declare them to be const?
> >>
> >> The _min and _max values shouldn't be changing: they're decided based
> >> on the various CONFIG options that calculate the valid min/maxes. Only
> >> mmap_rnd_bits itself should be changing.
> >
> > hmpf.
> >
> > From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Subject: include/linux/sysctl.h: make ctl_table.extra1/2 const
> >
> > Nothing should be altering these values. Declare the pointed-to values to
> > be const so we can actually use const values.
>
> No large objects except we do seem to have values that are stashed
> in extra1 that are cast to non-const types.
>
> Any chance you will do the work to hunt all of those down and modify
> the casts to preserve const or to remove the casts entirely?
Below. Most of it, anyway.
net is doing weird stuff, stashing very-much-non-const things into
extra1 and extra2. I don't see much point in sprinkling casts
everywhere to conceal this (ab)use. extra1 and extra2 clearly aren't
const, so I think I'll give up and sulk.
drivers/parport/procfs.c | 4 ++--
net/core/neighbour.c | 6 +++---
net/decnet/dn_dev.c | 2 +-
net/ipv4/devinet.c | 10 +++++-----
net/ipv6/addrconf.c | 12 +++++++-----
net/ipv6/ndisc.c | 2 +-
net/netfilter/ipvs/ip_vs_ctl.c | 2 +-
7 files changed, 20 insertions(+), 18 deletions(-)
diff -puN net/core/neighbour.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/core/neighbour.c
--- a/net/core/neighbour.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/core/neighbour.c
@@ -2915,8 +2915,8 @@ static void neigh_copy_dflt_parms(struct
static void neigh_proc_update(struct ctl_table *ctl, int write)
{
- struct net_device *dev = ctl->extra1;
- struct neigh_parms *p = ctl->extra2;
+ struct net_device *dev = (void *)ctl->extra1;
+ struct neigh_parms *p = (void *)ctl->extra2;
struct net *net = neigh_parms_net(p);
int index = (int *) ctl->data - p->data;
@@ -2999,7 +2999,7 @@ static int neigh_proc_base_reachable_tim
void __user *buffer,
size_t *lenp, loff_t *ppos)
{
- struct neigh_parms *p = ctl->extra2;
+ struct neigh_parms *p = (void *)ctl->extra2;
int ret;
if (strcmp(ctl->procname, "base_reachable_time") == 0)
diff -puN net/decnet/dn_dev.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/decnet/dn_dev.c
--- a/net/decnet/dn_dev.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/decnet/dn_dev.c
@@ -248,7 +248,7 @@ static int dn_forwarding_proc(struct ctl
size_t *lenp, loff_t *ppos)
{
#ifdef CONFIG_DECNET_ROUTER
- struct net_device *dev = table->extra1;
+ struct net_device *dev = (void *)table->extra1;
struct dn_dev *dn_db;
int err;
int tmp, old;
diff -puN net/ipv4/devinet.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/ipv4/devinet.c
--- a/net/ipv4/devinet.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/ipv4/devinet.c
@@ -2030,8 +2030,8 @@ static int devinet_conf_proc(struct ctl_
int new_value = *(int *)ctl->data;
if (write) {
- struct ipv4_devconf *cnf = ctl->extra1;
- struct net *net = ctl->extra2;
+ struct ipv4_devconf *cnf = (void *)ctl->extra1;
+ struct net *net = (void *)ctl->extra2;
int i = (int *)ctl->data - cnf->data;
int ifindex;
@@ -2077,7 +2077,7 @@ static int devinet_sysctl_forward(struct
int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
if (write && *valp != val) {
- struct net *net = ctl->extra2;
+ struct net *net = (void *)ctl->extra2;
if (valp != &IPV4_DEVCONF_DFLT(net, FORWARDING)) {
if (!rtnl_trylock()) {
@@ -2089,7 +2089,7 @@ static int devinet_sysctl_forward(struct
if (valp == &IPV4_DEVCONF_ALL(net, FORWARDING)) {
inet_forward_change(net);
} else {
- struct ipv4_devconf *cnf = ctl->extra1;
+ struct ipv4_devconf *cnf = (void *)ctl->extra1;
struct in_device *idev =
container_of(cnf, struct in_device, cnf);
if (*valp)
@@ -2117,7 +2117,7 @@ static int ipv4_doint_and_flush(struct c
int *valp = ctl->data;
int val = *valp;
int ret = proc_dointvec(ctl, write, buffer, lenp, ppos);
- struct net *net = ctl->extra2;
+ struct net *net = (void *)ctl->extra2;
if (write && *valp != val)
rt_cache_flush(net);
diff -puN net/ipv6/addrconf.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/ipv6/addrconf.c
--- a/net/ipv6/addrconf.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/ipv6/addrconf.c
@@ -5203,7 +5203,7 @@ static
int addrconf_sysctl_mtu(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
- struct inet6_dev *idev = ctl->extra1;
+ const struct inet6_dev *idev = ctl->extra1;
int min_mtu = IPV6_MIN_MTU;
struct ctl_table lctl;
@@ -5312,7 +5312,7 @@ int addrconf_sysctl_proxy_ndp(struct ctl
new = *valp;
if (write && old != new) {
- struct net *net = ctl->extra2;
+ struct net *net = (struct net *)ctl->extra2;
if (!rtnl_trylock())
return restart_syscall();
@@ -5326,8 +5326,9 @@ int addrconf_sysctl_proxy_ndp(struct ctl
NETCONFA_IFINDEX_ALL,
net->ipv6.devconf_all);
else {
- struct inet6_dev *idev = ctl->extra1;
+ struct inet6_dev *idev;
+ idev = (struct inet6_dev *)ctl->extra1;
inet6_netconf_notify_devconf(net, NETCONFA_PROXY_NEIGH,
idev->dev->ifindex,
&idev->cnf);
@@ -5346,7 +5347,7 @@ static int addrconf_sysctl_stable_secret
struct in6_addr addr;
char str[IPV6_MAX_STRLEN];
struct ctl_table lctl = *ctl;
- struct net *net = ctl->extra2;
+ const struct net *net = ctl->extra2;
struct ipv6_stable_secret *secret = ctl->data;
if (&net->ipv6.devconf_all->stable_secret == ctl->data)
@@ -5396,8 +5397,9 @@ static int addrconf_sysctl_stable_secret
}
}
} else {
- struct inet6_dev *idev = ctl->extra1;
+ struct inet6_dev *idev;
+ idev = (struct inet6_dev *)ctl->extra1;
idev->addr_gen_mode = IN6_ADDR_GEN_MODE_STABLE_PRIVACY;
}
diff -puN net/ipv6/ndisc.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/ipv6/ndisc.c
--- a/net/ipv6/ndisc.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/ipv6/ndisc.c
@@ -1738,7 +1738,7 @@ static void ndisc_warn_deprecated_sysctl
int ndisc_ifinfo_sysctl_change(struct ctl_table *ctl, int write, void __user *buffer, size_t *lenp, loff_t *ppos)
{
- struct net_device *dev = ctl->extra1;
+ const struct net_device *dev = ctl->extra1;
struct inet6_dev *idev;
int ret;
diff -puN net/netfilter/ipvs/ip_vs_ctl.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix net/netfilter/ipvs/ip_vs_ctl.c
--- a/net/netfilter/ipvs/ip_vs_ctl.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1608,7 +1608,7 @@ static int
proc_do_defense_mode(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
- struct netns_ipvs *ipvs = table->extra2;
+ struct netns_ipvs *ipvs = (void *)table->extra2;
int *valp = table->data;
int val = *valp;
int rc;
diff -puN drivers/parport/procfs.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix drivers/parport/procfs.c
--- a/drivers/parport/procfs.c~include-linux-sysctlh-make-ctl_tableextra1-2-const-fix
+++ a/drivers/parport/procfs.c
@@ -35,7 +35,7 @@
static int do_active_device(struct ctl_table *table, int write,
void __user *result, size_t *lenp, loff_t *ppos)
{
- struct parport *port = (struct parport *)table->extra1;
+ const struct parport *port = table->extra1;
char buffer[256];
struct pardevice *dev;
int len = 0;
@@ -72,7 +72,7 @@ static int do_active_device(struct ctl_t
static int do_autoprobe(struct ctl_table *table, int write,
void __user *result, size_t *lenp, loff_t *ppos)
{
- struct parport_device_info *info = table->extra2;
+ const struct parport_device_info *info = table->extra2;
const char *str;
char buffer[256];
int len = 0;
_
--
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