| Message ID | 20180530003525.GA18642@beast |
|---|---|
| State | Changes Requested |
| Delegated to: | Pablo Neira |
| Headers | show |
| Series | netfilter: nfnetlink: Remove VLA usage | expand |
Kees Cook <keescook@chromium.org> wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > allocates the maximum size expected for all possible attrs and adds > a sanity-check to make sure nothing gets out of sync. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > net/netfilter/nfnetlink.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c > index 03ead8a9e90c..0cb395f9627e 100644 > --- a/net/netfilter/nfnetlink.c > +++ b/net/netfilter/nfnetlink.c > @@ -28,6 +28,7 @@ > > #include <net/netlink.h> > #include <linux/netfilter/nfnetlink.h> > +#include <linux/netfilter/nf_tables.h> > > const struct nfnetlink_subsystem __rcu *subsys; > @@ -185,11 +191,17 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, > { > int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); > u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); > - struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; > + struct nlattr *cda[NFTA_MAX_ATTR + 1]; > struct nlattr *attr = (void *)nlh + min_len; > int attrlen = nlh->nlmsg_len - min_len; > __u8 subsys_id = NFNL_SUBSYS_ID(type); > > + /* Sanity-check NFTA_MAX_ATTR */ > + if (ss->cb[cb_id].attr_count > NFTA_MAX_ATTR) { > + rcu_read_unlock(); > + return -ENOMEM; > + } Would you mind also adding check to nfnetlink_subsys_register, plus WARN()? That way we'll see that NFTA_MAX_ATTR isn't large enough by virtue of registration rather than actual use. Other than that this looks fine to me. -- 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
On Tue, May 29, 2018 at 05:35:25PM -0700, Kees Cook wrote: > In the quest to remove all stack VLA usage from the kernel[1], this > allocates the maximum size expected for all possible attrs and adds > a sanity-check to make sure nothing gets out of sync. > > [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com > > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > net/netfilter/nfnetlink.c | 22 ++++++++++++++++++++-- > 1 file changed, 20 insertions(+), 2 deletions(-) > > diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c > index 03ead8a9e90c..0cb395f9627e 100644 > --- a/net/netfilter/nfnetlink.c > +++ b/net/netfilter/nfnetlink.c > @@ -28,6 +28,7 @@ > > #include <net/netlink.h> > #include <linux/netfilter/nfnetlink.h> > +#include <linux/netfilter/nf_tables.h> > > MODULE_LICENSE("GPL"); > MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); > @@ -37,6 +38,11 @@ MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); > rcu_dereference_protected(table[(id)].subsys, \ > lockdep_nfnl_is_held((id))) > > +#define NFTA_MAX_ATTR max(max(max(NFTA_CHAIN_MAX, NFTA_FLOWTABLE_MAX),\ > + max(NFTA_OBJ_MAX, NFTA_RULE_MAX)), \ > + max(NFTA_TABLE_MAX, \ > + max(NFTA_SET_ELEM_LIST_MAX, NFTA_SET_MAX))) This is very specific of nftables, there are other nf subsystems using nfnetlink that may go over this maximum attribute value (grep from "struct nfnetlink_subsystem"). To remove the VLA, I think we need an artificial maximum attribute that reasonably large enough. -- 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
On Wed, May 30, 2018 at 2:52 AM, Pablo Neira Ayuso <pablo@netfilter.org> wrote: > On Tue, May 29, 2018 at 05:35:25PM -0700, Kees Cook wrote: >> In the quest to remove all stack VLA usage from the kernel[1], this >> allocates the maximum size expected for all possible attrs and adds >> a sanity-check to make sure nothing gets out of sync. >> >> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com >> >> Signed-off-by: Kees Cook <keescook@chromium.org> >> --- >> net/netfilter/nfnetlink.c | 22 ++++++++++++++++++++-- >> 1 file changed, 20 insertions(+), 2 deletions(-) >> >> diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c >> index 03ead8a9e90c..0cb395f9627e 100644 >> --- a/net/netfilter/nfnetlink.c >> +++ b/net/netfilter/nfnetlink.c >> @@ -28,6 +28,7 @@ >> >> #include <net/netlink.h> >> #include <linux/netfilter/nfnetlink.h> >> +#include <linux/netfilter/nf_tables.h> >> >> MODULE_LICENSE("GPL"); >> MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); >> @@ -37,6 +38,11 @@ MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); >> rcu_dereference_protected(table[(id)].subsys, \ >> lockdep_nfnl_is_held((id))) >> >> +#define NFTA_MAX_ATTR max(max(max(NFTA_CHAIN_MAX, NFTA_FLOWTABLE_MAX),\ >> + max(NFTA_OBJ_MAX, NFTA_RULE_MAX)), \ >> + max(NFTA_TABLE_MAX, \ >> + max(NFTA_SET_ELEM_LIST_MAX, NFTA_SET_MAX))) > > This is very specific of nftables, there are other nf subsystems using > nfnetlink that may go over this maximum attribute value (grep from > "struct nfnetlink_subsystem"). Oops, yes. I see that now. > To remove the VLA, I think we need an artificial maximum attribute > that reasonably large enough. git grep insanity: $ for i in $(git grep -A10 'static .*struct nfnetlink_subsystem' | \ grep '\.cb\b' | awk '{print $NF}' | cut -d, -f1) do git grep -A100 'static .*'"$i\b"; done | \ grep '\.attr_count\b' | awk -F= '{print $NF}' | \ sed -e 's/ //g' | cut -d, -f1 | sort -u and manual counting gets me: CTA_EXPECT_MAX 12 CTA_MAX 25 CTA_TIMEOUT_MAX 6 IPSET_ATTR_CMD_MAX 11 NFACCT_MAX 9 NFCTH_MAX 7 NFQA_CFG_MAX 6 NFQA_MAX 21 NFTA_CHAIN_MAX 10 NFTA_COMPAT_MAX 4 NFTA_OBJ_MAX 8 NFTA_RULE_MAX 10 NFTA_SET_ELEM_LIST_MAX 5 NFTA_SET_MAX 17 NFTA_TABLE_MAX 6 NFULA_CFG_MAX 7 NFULA_MAX 20 OSF_ATTR_MAX 2 How about 32? As Florian suggested, I'll add the check in nfnetlink_subsys_register() with a WARN(). -Kees
diff --git a/net/netfilter/nfnetlink.c b/net/netfilter/nfnetlink.c index 03ead8a9e90c..0cb395f9627e 100644 --- a/net/netfilter/nfnetlink.c +++ b/net/netfilter/nfnetlink.c @@ -28,6 +28,7 @@ #include <net/netlink.h> #include <linux/netfilter/nfnetlink.h> +#include <linux/netfilter/nf_tables.h> MODULE_LICENSE("GPL"); MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); @@ -37,6 +38,11 @@ MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); rcu_dereference_protected(table[(id)].subsys, \ lockdep_nfnl_is_held((id))) +#define NFTA_MAX_ATTR max(max(max(NFTA_CHAIN_MAX, NFTA_FLOWTABLE_MAX),\ + max(NFTA_OBJ_MAX, NFTA_RULE_MAX)), \ + max(NFTA_TABLE_MAX, \ + max(NFTA_SET_ELEM_LIST_MAX, NFTA_SET_MAX))) + static struct { struct mutex mutex; const struct nfnetlink_subsystem __rcu *subsys; @@ -185,11 +191,17 @@ static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh, { int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); - struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; + struct nlattr *cda[NFTA_MAX_ATTR + 1]; struct nlattr *attr = (void *)nlh + min_len; int attrlen = nlh->nlmsg_len - min_len; __u8 subsys_id = NFNL_SUBSYS_ID(type); + /* Sanity-check NFTA_MAX_ATTR */ + if (ss->cb[cb_id].attr_count > NFTA_MAX_ATTR) { + rcu_read_unlock(); + return -ENOMEM; + } + err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen, ss->cb[cb_id].policy, extack); if (err < 0) { @@ -379,10 +391,16 @@ static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh, { int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); u8 cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); - struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; + struct nlattr *cda[NFTA_MAX_ATTR + 1]; struct nlattr *attr = (void *)nlh + min_len; int attrlen = nlh->nlmsg_len - min_len; + /* Sanity-check NFTA_MAX_ATTR */ + if (ss->cb[cb_id].attr_count > NFTA_MAX_ATTR) { + err = -ENOMEM; + goto ack; + } + err = nla_parse(cda, ss->cb[cb_id].attr_count, attr, attrlen, ss->cb[cb_id].policy, NULL); if (err < 0)
In the quest to remove all stack VLA usage from the kernel[1], this allocates the maximum size expected for all possible attrs and adds a sanity-check to make sure nothing gets out of sync. [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com Signed-off-by: Kees Cook <keescook@chromium.org> --- net/netfilter/nfnetlink.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-)