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, 320 insertions, 0 deletions

diff --git a/include/net/act_api.h b/include/net/act_api.h
new file mode 100644
index 000000000..fd03f6319
--- /dev/null
+++ b/include/net/act_api.h
@@ -0,0 +1,320 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __NET_ACT_API_H
+#define __NET_ACT_API_H
+
+/*
+ * Public action API for classifiers/qdiscs
+*/
+
+#include <linux/refcount.h>
+#include <net/flow_offload.h>
+#include <net/sch_generic.h>
+#include <net/pkt_sched.h>
+#include <net/net_namespace.h>
+#include <net/netns/generic.h>
+
+struct tcf_idrinfo {
+	struct mutex	lock;
+	struct idr	action_idr;
+	struct net	*net;
+};
+
+struct tc_action_ops;
+
+struct tc_action {
+	const struct tc_action_ops	*ops;
+	__u32				type; /* for backward compat(TCA_OLD_COMPAT) */
+	struct tcf_idrinfo		*idrinfo;
+
+	u32				tcfa_index;
+	refcount_t			tcfa_refcnt;
+	atomic_t			tcfa_bindcnt;
+	int				tcfa_action;
+	struct tcf_t			tcfa_tm;
+	struct gnet_stats_basic_sync	tcfa_bstats;
+	struct gnet_stats_basic_sync	tcfa_bstats_hw;
+
+	atomic_t			tcfa_drops;
+	atomic_t			tcfa_overlimits;
+
+	struct net_rate_estimator __rcu *tcfa_rate_est;
+	spinlock_t			tcfa_lock;
+	struct gnet_stats_basic_sync __percpu *cpu_bstats;
+	struct gnet_stats_basic_sync __percpu *cpu_bstats_hw;
+	struct gnet_stats_queue __percpu *cpu_qstats;
+	struct tc_cookie	__rcu *user_cookie;
+	struct tcf_chain	__rcu *goto_chain;
+	u32			tcfa_flags;
+	struct rcu_head         tcfa_rcu;
+	u8			hw_stats;
+	u8			used_hw_stats;
+	bool			used_hw_stats_valid;
+	u32			in_hw_count;
+};
+#define tcf_index	common.tcfa_index
+#define tcf_refcnt	common.tcfa_refcnt
+#define tcf_bindcnt	common.tcfa_bindcnt
+#define tcf_action	common.tcfa_action
+#define tcf_tm		common.tcfa_tm
+#define tcf_bstats	common.tcfa_bstats
+#define tcf_rate_est	common.tcfa_rate_est
+#define tcf_lock	common.tcfa_lock
+
+#define TCA_ACT_HW_STATS_ANY (TCA_ACT_HW_STATS_IMMEDIATE | \
+			      TCA_ACT_HW_STATS_DELAYED)
+
+/* Reserve 16 bits for user-space. See TCA_ACT_FLAGS_NO_PERCPU_STATS. */
+#define TCA_ACT_FLAGS_USER_BITS 16
+#define TCA_ACT_FLAGS_USER_MASK 0xffff
+#define TCA_ACT_FLAGS_POLICE	(1U << TCA_ACT_FLAGS_USER_BITS)
+#define TCA_ACT_FLAGS_BIND	(1U << (TCA_ACT_FLAGS_USER_BITS + 1))
+#define TCA_ACT_FLAGS_REPLACE	(1U << (TCA_ACT_FLAGS_USER_BITS + 2))
+#define TCA_ACT_FLAGS_NO_RTNL	(1U << (TCA_ACT_FLAGS_USER_BITS + 3))
+#define TCA_ACT_FLAGS_AT_INGRESS	(1U << (TCA_ACT_FLAGS_USER_BITS + 4))
+#define TCA_ACT_FLAGS_AT_INGRESS_OR_CLSACT	(1U << (TCA_ACT_FLAGS_USER_BITS + 5))
+
+/* Update lastuse only if needed, to avoid dirtying a cache line.
+ * We use a temp variable to avoid fetching jiffies twice.
+ */
+static inline void tcf_lastuse_update(struct tcf_t *tm)
+{
+	unsigned long now = jiffies;
+
+	if (READ_ONCE(tm->lastuse) != now)
+		WRITE_ONCE(tm->lastuse, now);
+	if (unlikely(!READ_ONCE(tm->firstuse)))
+		WRITE_ONCE(tm->firstuse, now);
+}
+
+static inline void tcf_tm_dump(struct tcf_t *dtm, const struct tcf_t *stm)
+{
+	unsigned long firstuse, now = jiffies;
+
+	dtm->install = jiffies_to_clock_t(now - READ_ONCE(stm->install));
+	dtm->lastuse = jiffies_to_clock_t(now - READ_ONCE(stm->lastuse));
+
+	firstuse = READ_ONCE(stm->firstuse);
+	dtm->firstuse = firstuse ?
+		jiffies_to_clock_t(now - firstuse) : 0;
+
+	dtm->expires = jiffies_to_clock_t(READ_ONCE(stm->expires));
+}
+
+static inline enum flow_action_hw_stats tc_act_hw_stats(u8 hw_stats)
+{
+	if (WARN_ON_ONCE(hw_stats > TCA_ACT_HW_STATS_ANY))
+		return FLOW_ACTION_HW_STATS_DONT_CARE;
+	else if (!hw_stats)
+		return FLOW_ACTION_HW_STATS_DISABLED;
+
+	return hw_stats;
+}
+
+typedef void (*tc_action_priv_destructor)(void *priv);
+
+struct tc_action_ops {
+	struct list_head head;
+	char    kind[IFNAMSIZ];
+	enum tca_id  id; /* identifier should match kind */
+	unsigned int	net_id;
+	size_t	size;
+	struct module		*owner;
+	int     (*act)(struct sk_buff *, const struct tc_action *,
+		       struct tcf_result *); /* called under RCU BH lock*/
+	int     (*dump)(struct sk_buff *, struct tc_action *, int, int);
+	void	(*cleanup)(struct tc_action *);
+	int     (*lookup)(struct net *net, struct tc_action **a, u32 index);
+	int     (*init)(struct net *net, struct nlattr *nla,
+			struct nlattr *est, struct tc_action **act,
+			struct tcf_proto *tp,
+			u32 flags, struct netlink_ext_ack *extack);
+	int     (*walk)(struct net *, struct sk_buff *,
+			struct netlink_callback *, int,
+			const struct tc_action_ops *,
+			struct netlink_ext_ack *);
+	void	(*stats_update)(struct tc_action *, u64, u64, u64, u64, bool);
+	size_t  (*get_fill_size)(const struct tc_action *act);
+	struct net_device *(*get_dev)(const struct tc_action *a,
+				      tc_action_priv_destructor *destructor);
+	struct psample_group *
+	(*get_psample_group)(const struct tc_action *a,
+			     tc_action_priv_destructor *destructor);
+	int     (*offload_act_setup)(struct tc_action *act, void *entry_data,
+				     u32 *index_inc, bool bind,
+				     struct netlink_ext_ack *extack);
+};
+
+#ifdef CONFIG_NET_CLS_ACT
+
+#define ACT_P_BOUND 0
+#define ACT_P_CREATED 1
+#define ACT_P_DELETED 1
+
+struct tc_action_net {
+	struct tcf_idrinfo *idrinfo;
+	const struct tc_action_ops *ops;
+};
+
+static inline
+int tc_action_net_init(struct net *net, struct tc_action_net *tn,
+		       const struct tc_action_ops *ops)
+{
+	int err = 0;
+
+	tn->idrinfo = kmalloc_obj(*tn->idrinfo);
+	if (!tn->idrinfo)
+		return -ENOMEM;
+	tn->ops = ops;
+	tn->idrinfo->net = net;
+	mutex_init(&tn->idrinfo->lock);
+	idr_init(&tn->idrinfo->action_idr);
+	return err;
+}
+
+void tcf_idrinfo_destroy(const struct tc_action_ops *ops,
+			 struct tcf_idrinfo *idrinfo);
+
+static inline void tc_action_net_exit(struct list_head *net_list,
+				      unsigned int id)
+{
+	struct net *net;
+
+	list_for_each_entry(net, net_list, exit_list) {
+		struct tc_action_net *tn = net_generic(net, id);
+
+		tcf_idrinfo_destroy(tn->ops, tn->idrinfo);
+		kfree(tn->idrinfo);
+	}
+}
+
+int tcf_generic_walker(struct tc_action_net *tn, struct sk_buff *skb,
+		       struct netlink_callback *cb, int type,
+		       const struct tc_action_ops *ops,
+		       struct netlink_ext_ack *extack);
+int tcf_idr_search(struct tc_action_net *tn, struct tc_action **a, u32 index);
+int tcf_idr_create(struct tc_action_net *tn, u32 index, struct nlattr *est,
+		   struct tc_action **a, const struct tc_action_ops *ops,
+		   int bind, bool cpustats, u32 flags);
+int tcf_idr_create_from_flags(struct tc_action_net *tn, u32 index,
+			      struct nlattr *est, struct tc_action **a,
+			      const struct tc_action_ops *ops, int bind,
+			      u32 flags);
+void tcf_idr_insert_many(struct tc_action *actions[], int init_res[]);
+void tcf_idr_cleanup(struct tc_action_net *tn, u32 index);
+int tcf_idr_check_alloc(struct tc_action_net *tn, u32 *index,
+			struct tc_action **a, int bind);
+int tcf_idr_release(struct tc_action *a, bool bind);
+
+int tcf_register_action(struct tc_action_ops *a, struct pernet_operations *ops);
+int tcf_unregister_action(struct tc_action_ops *a,
+			  struct pernet_operations *ops);
+#define NET_ACT_ALIAS_PREFIX "net-act-"
+#define MODULE_ALIAS_NET_ACT(kind)	MODULE_ALIAS(NET_ACT_ALIAS_PREFIX kind)
+int tcf_action_destroy(struct tc_action *actions[], int bind);
+int tcf_action_exec(struct sk_buff *skb, struct tc_action **actions,
+		    int nr_actions, struct tcf_result *res);
+int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
+		    struct nlattr *est,
+		    struct tc_action *actions[], int init_res[], size_t *attr_size,
+		    u32 flags, u32 fl_flags, struct netlink_ext_ack *extack);
+struct tc_action_ops *tc_action_load_ops(struct nlattr *nla, u32 flags,
+					 struct netlink_ext_ack *extack);
+struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp,
+				    struct nlattr *nla, struct nlattr *est,
+				    struct tc_action_ops *a_o, int *init_res,
+				    u32 flags, struct netlink_ext_ack *extack);
+int tcf_action_dump(struct sk_buff *skb, struct tc_action *actions[], int bind,
+		    int ref, bool terse);
+int tcf_action_dump_old(struct sk_buff *skb, struct tc_action *a, int, int);
+
+static inline void tcf_action_update_bstats(struct tc_action *a,
+					    struct sk_buff *skb)
+{
+	if (likely(a->cpu_bstats)) {
+		bstats_update(this_cpu_ptr(a->cpu_bstats), skb);
+		return;
+	}
+	spin_lock(&a->tcfa_lock);
+	bstats_update(&a->tcfa_bstats, skb);
+	spin_unlock(&a->tcfa_lock);
+}
+
+static inline void tcf_action_inc_drop_qstats(struct tc_action *a)
+{
+	if (likely(a->cpu_qstats)) {
+		qstats_cpu_drop_inc(a->cpu_qstats);
+		return;
+	}
+	atomic_inc(&a->tcfa_drops);
+}
+
+static inline void tcf_action_inc_overlimit_qstats(struct tc_action *a)
+{
+	if (likely(a->cpu_qstats)) {
+		qstats_cpu_overlimit_inc(a->cpu_qstats);
+		return;
+	}
+	atomic_inc(&a->tcfa_overlimits);
+}
+
+void tcf_action_update_stats(struct tc_action *a, u64 bytes, u64 packets,
+			     u64 drops, bool hw);
+int tcf_action_copy_stats(struct sk_buff *, struct tc_action *, int);
+
+int tcf_action_update_hw_stats(struct tc_action *action);
+int tcf_action_reoffload_cb(flow_indr_block_bind_cb_t *cb,
+			    void *cb_priv, bool add);
+int tcf_action_check_ctrlact(int action, struct tcf_proto *tp,
+			     struct tcf_chain **handle,
+			     struct netlink_ext_ack *newchain);
+struct tcf_chain *tcf_action_set_ctrlact(struct tc_action *a, int action,
+					 struct tcf_chain *newchain);
+
+/* Range check for a control action supplied by user space.
+ *
+ * This is the same test tcf_action_check_ctrlact() applies to the primary
+ * control action, factored out for the *fallback* control actions
+ * (act_gact's TCA_GACT_PROB.paction and act_police's TCA_POLICE_RESULT),
+ * which must not reach tcf_action_check_ctrlact() because they have no
+ * goto_chain to allocate.  Without it, user space can store kernel-internal
+ * verdicts such as TC_ACT_CONSUMED, which is TC_ACT_VALUE_MAX + 1 and is
+ * deliberately not part of the UAPI value range.
+ */
+static inline bool tcf_action_valid(int action)
+{
+	int opcode = TC_ACT_EXT_OPCODE(action);
+
+	if (!opcode)
+		return action <= TC_ACT_VALUE_MAX;
+	return opcode <= TC_ACT_EXT_OPCODE_MAX || action == TC_ACT_UNSPEC;
+}
+
+#ifdef CONFIG_INET
+DECLARE_STATIC_KEY_FALSE(tcf_frag_xmit_count);
+#endif
+
+int tcf_dev_queue_xmit(struct sk_buff *skb, int (*xmit)(struct sk_buff *skb));
+
+#else /* !CONFIG_NET_CLS_ACT */
+
+static inline int tcf_action_reoffload_cb(flow_indr_block_bind_cb_t *cb,
+					  void *cb_priv, bool add) {
+	return 0;
+}
+
+#endif /* CONFIG_NET_CLS_ACT */
+
+static inline void tcf_action_stats_update(struct tc_action *a, u64 bytes,
+					   u64 packets, u64 drops,
+					   u64 lastuse, bool hw)
+{
+#ifdef CONFIG_NET_CLS_ACT
+	if (!a->ops->stats_update)
+		return;
+
+	a->ops->stats_update(a, bytes, packets, drops, lastuse, hw);
+#endif
+}
+
+
+#endif