selftests/bpf: Test packet range of pointers sharing an idgrafted

Add tests where two packet pointers share an id and tightening one
pointer's umax from its var_off would put it less than their constant
distance from the other's umax: with an index & 0x38 capped at 50, the
base pointer keeps umax 50, so the pointer 8 bytes further on must keep
umax 58, even though its known bits allow at most 56.

These refused a valid program or accepted an out-of-bounds access before
the fix:

- check the advanced copy, load through the base: valid, was refused;
- check the base, load the byte at base + 1 through a copy advanced by
  8: was accepted;
- check base + 4, load 4 bytes at base + 2 through base + 8: reads two
  bytes past the checked range, was accepted;
- the same as the second with data_meta pointers checked against data:
  was accepted.

These pass with and without the fix and cover nearby paths:

- subtract an unknown scalar from a checked pointer and load below it
  (the range is kept across a new id);
- reach a load through two paths whose checks cover 8 and 7 bytes after
  the loaded pointer; the second path must not be pruned by the first;
- spill a copy of a pointer, check the pointer, fill the copy and load
  one byte past the checked range: the load is refused, and the copy
  has the range of the check.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20261001145255.855630-2-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 232 insertions, 0 deletions

diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
new file mode 100644
index 000000000..c6b94790f
--- /dev/null
+++ b/include/net/fib_rules.h
@@ -0,0 +1,232 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_FIB_RULES_H
+#define __NET_FIB_RULES_H
+
+#include <linux/types.h>
+#include <linux/slab.h>
+#include <linux/netdevice.h>
+#include <linux/fib_rules.h>
+#include <linux/refcount.h>
+#include <net/flow.h>
+#include <net/rtnetlink.h>
+#include <net/fib_notifier.h>
+#include <linux/indirect_call_wrapper.h>
+
+struct fib_kuid_range {
+	kuid_t start;
+	kuid_t end;
+};
+
+struct fib_rule {
+	struct list_head	list;
+	int			iifindex;
+	int			oifindex;
+	u32			mark;
+	u32			mark_mask;
+	u32			flags;
+	u32			table;
+	u8			action;
+	u8			l3mdev;
+	u8                      proto;
+	u8			ip_proto;
+	u32			target;
+	__be64			tun_id;
+	struct fib_rule __rcu	*ctarget;
+	struct net		*fr_net;
+
+	refcount_t		refcnt;
+	u32			pref;
+	int			suppress_ifgroup;
+	int			suppress_prefixlen;
+	char			iifname[IFNAMSIZ];
+	char			oifname[IFNAMSIZ];
+	struct fib_kuid_range	uid_range;
+	struct fib_rule_port_range	sport_range;
+	struct fib_rule_port_range	dport_range;
+	u16			sport_mask;
+	u16			dport_mask;
+	u8                      iif_is_l3_master;
+	u8                      oif_is_l3_master;
+	struct rcu_head		rcu;
+};
+
+struct fib_lookup_arg {
+	void			*lookup_ptr;
+	const void		*lookup_data;
+	void			*result;
+	struct fib_rule		*rule;
+	u32			table;
+	int			flags;
+#define FIB_LOOKUP_NOREF		1
+#define FIB_LOOKUP_IGNORE_LINKSTATE	2
+};
+
+struct fib_rules_ops {
+	int			family;
+	struct list_head	list;
+	int			rule_size;
+	int			addr_size;
+	int			unresolved_rules;
+	int			nr_goto_rules;
+	unsigned int		fib_rules_seq;
+
+	int			(*action)(struct fib_rule *,
+					  struct flowi *, int,
+					  struct fib_lookup_arg *);
+	bool			(*suppress)(struct fib_rule *, int,
+					    struct fib_lookup_arg *);
+	int			(*match)(struct fib_rule *,
+					 struct flowi *, int);
+	int			(*configure)(struct fib_rule *,
+					     struct sk_buff *,
+					     struct fib_rule_hdr *,
+					     struct nlattr **,
+					     struct netlink_ext_ack *);
+	void			(*delete)(struct fib_rule *);
+	int			(*compare)(struct fib_rule *,
+					   struct fib_rule_hdr *,
+					   struct nlattr **);
+	int			(*fill)(struct fib_rule *, struct sk_buff *,
+					struct fib_rule_hdr *);
+	size_t			(*nlmsg_payload)(struct fib_rule *);
+
+	/* Called after modifications to the rules set, must flush
+	 * the route cache if one exists. */
+	void			(*flush_cache)(struct fib_rules_ops *ops);
+	bool			(*need_rtnl)(struct net *net);
+
+	int			nlgroup;
+	struct list_head	rules_list;
+	struct module		*owner;
+	struct net		*fro_net;
+	struct mutex		lock;
+	struct rcu_head		rcu;
+};
+
+struct fib_rule_notifier_info {
+	struct fib_notifier_info info; /* must be first */
+	struct fib_rule *rule;
+};
+
+static inline void fib_rule_get(struct fib_rule *rule)
+{
+	refcount_inc(&rule->refcnt);
+}
+
+static inline bool fib_rule_get_safe(struct fib_rule *rule)
+{
+	return refcount_inc_not_zero(&rule->refcnt);
+}
+
+static inline void fib_rule_put(struct fib_rule *rule)
+{
+	if (refcount_dec_and_test(&rule->refcnt))
+		kfree_rcu(rule, rcu);
+}
+
+#ifdef CONFIG_NET_L3_MASTER_DEV
+static inline u32 fib_rule_get_table(struct fib_rule *rule,
+				     struct fib_lookup_arg *arg)
+{
+	return rule->l3mdev ? arg->table : rule->table;
+}
+#else
+static inline u32 fib_rule_get_table(struct fib_rule *rule,
+				     struct fib_lookup_arg *arg)
+{
+	return rule->table;
+}
+#endif
+
+static inline u32 frh_get_table(struct fib_rule_hdr *frh, struct nlattr **nla)
+{
+	if (nla[FRA_TABLE])
+		return nla_get_u32(nla[FRA_TABLE]);
+	return frh->table;
+}
+
+static inline bool fib_rule_port_range_set(const struct fib_rule_port_range *range)
+{
+	return range->start != 0 && range->end != 0;
+}
+
+static inline bool fib_rule_port_inrange(const struct fib_rule_port_range *a,
+					 __be16 port)
+{
+	return ntohs(port) >= a->start &&
+		ntohs(port) <= a->end;
+}
+
+static inline bool fib_rule_port_match(const struct fib_rule_port_range *range,
+				       u16 port_mask, __be16 port)
+{
+	if ((range->start ^ ntohs(port)) & port_mask)
+		return false;
+	if (!port_mask && fib_rule_port_range_set(range) &&
+	    !fib_rule_port_inrange(range, port))
+		return false;
+	return true;
+}
+
+static inline bool fib_rule_port_range_valid(const struct fib_rule_port_range *a)
+{
+	return a->start != 0 && a->end != 0 && a->end < 0xffff &&
+		a->start <= a->end;
+}
+
+static inline bool fib_rule_port_range_compare(struct fib_rule_port_range *a,
+					       struct fib_rule_port_range *b)
+{
+	return a->start == b->start &&
+		a->end == b->end;
+}
+
+static inline bool
+fib_rule_port_is_range(const struct fib_rule_port_range *range)
+{
+	return range->start != range->end;
+}
+
+static inline bool fib_rule_requires_fldissect(struct fib_rule *rule)
+{
+	return rule->iifindex != LOOPBACK_IFINDEX && (rule->ip_proto ||
+		fib_rule_port_range_set(&rule->sport_range) ||
+		fib_rule_port_range_set(&rule->dport_range));
+}
+
+struct fib_rules_ops *fib_rules_register(const struct fib_rules_ops *,
+					 struct net *);
+void fib_rules_unregister(struct fib_rules_ops *);
+
+int fib_rules_lookup(struct fib_rules_ops *, struct flowi *, int flags,
+		     struct fib_lookup_arg *);
+int fib_default_rule_add(struct fib_rules_ops *, u32 pref, u32 table);
+bool fib_rule_matchall(const struct fib_rule *rule);
+int fib_rules_dump(struct net *net, struct notifier_block *nb, int family,
+		   struct netlink_ext_ack *extack);
+unsigned int fib_rules_seq_read(const struct net *net, int family);
+
+int fib_newrule(struct net *net, struct sk_buff *skb, struct nlmsghdr *nlh,
+		struct netlink_ext_ack *extack, bool rtnl_held);
+int fib_delrule(struct net *net, struct sk_buff *skb, struct nlmsghdr *nlh,
+		struct netlink_ext_ack *extack, bool rtnl_held);
+
+INDIRECT_CALLABLE_DECLARE(int fib6_rule_match(struct fib_rule *rule,
+					    struct flowi *fl, int flags));
+INDIRECT_CALLABLE_DECLARE(int fib4_rule_match(struct fib_rule *rule,
+					    struct flowi *fl, int flags));
+
+INDIRECT_CALLABLE_DECLARE(int fib6_rule_action(struct fib_rule *rule,
+			    struct flowi *flp, int flags,
+			    struct fib_lookup_arg *arg));
+INDIRECT_CALLABLE_DECLARE(int fib4_rule_action(struct fib_rule *rule,
+			    struct flowi *flp, int flags,
+			    struct fib_lookup_arg *arg));
+
+INDIRECT_CALLABLE_DECLARE(bool fib6_rule_suppress(struct fib_rule *rule,
+						int flags,
+						struct fib_lookup_arg *arg));
+INDIRECT_CALLABLE_DECLARE(bool fib4_rule_suppress(struct fib_rule *rule,
+						int flags,
+						struct fib_lookup_arg *arg));
+#endif