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, 154 insertions, 0 deletions

diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
new file mode 100644
index 000000000..414e9adf4
--- /dev/null
+++ b/include/net/inetpeer.h
@@ -0,0 +1,154 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *		INETPEER - A storage for permanent information about peers
+ *
+ *  Authors:	Andrey V. Savochkin <saw@msu.ru>
+ */
+
+#ifndef _NET_INETPEER_H
+#define _NET_INETPEER_H
+
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/spinlock.h>
+#include <linux/rtnetlink.h>
+#include <net/ipv6.h>
+#include <linux/atomic.h>
+
+/* IPv4 address key for cache lookups */
+struct ipv4_addr_key {
+	__be32	addr;
+	int	vif;
+};
+
+#define INETPEER_MAXKEYSZ   (sizeof(struct in6_addr) / sizeof(u32))
+
+struct inetpeer_addr {
+	union {
+		struct ipv4_addr_key	a4;
+		struct in6_addr		a6;
+		u32			key[INETPEER_MAXKEYSZ];
+	};
+	__u16				family;
+};
+
+struct inet_peer {
+	struct rb_node		rb_node;
+	u64			hash;
+	struct inetpeer_addr	daddr;
+
+	u32			metrics[RTAX_MAX];
+	u32			rate_tokens;	/* rate limiting for ICMP */
+	u32			n_redirects;
+	unsigned long		rate_last;
+	/*
+	 * Once inet_peer is queued for deletion (refcnt == 0), following field
+	 * is not available: rid
+	 * We can share memory with rcu_head to help keep inet_peer small.
+	 */
+	union {
+		struct {
+			atomic_t			rid;		/* Frag reception counter */
+		};
+		struct rcu_head         rcu;
+	};
+
+	/* following fields might be frequently dirtied */
+	__u32			dtime;	/* the time of last use of not referenced entries */
+	refcount_t		refcnt;
+};
+
+struct inet_peer_base {
+	struct rb_root		rb_root;
+	seqlock_t		lock;
+	int			total;
+};
+
+void inet_peer_base_init(struct inet_peer_base *);
+
+void inet_initpeers(void) __init;
+
+#define INETPEER_METRICS_NEW	(~(u32) 0)
+
+static inline void inetpeer_set_addr_v4(struct inetpeer_addr *iaddr, __be32 ip)
+{
+	iaddr->a4.addr = ip;
+	iaddr->a4.vif = 0;
+	iaddr->family = AF_INET;
+}
+
+static inline __be32 inetpeer_get_addr_v4(struct inetpeer_addr *iaddr)
+{
+	return iaddr->a4.addr;
+}
+
+static inline void inetpeer_set_addr_v6(struct inetpeer_addr *iaddr,
+					struct in6_addr *in6)
+{
+	iaddr->a6 = *in6;
+	iaddr->family = AF_INET6;
+}
+
+static inline struct in6_addr *inetpeer_get_addr_v6(struct inetpeer_addr *iaddr)
+{
+	return &iaddr->a6;
+}
+
+/* can be called with or without local BH being disabled */
+struct inet_peer *inet_getpeer(struct inet_peer_base *base,
+			       const struct inetpeer_addr *daddr);
+
+static inline struct inet_peer *inet_getpeer_v4(struct inet_peer_base *base,
+						__be32 v4daddr,
+						int vif)
+{
+	struct inetpeer_addr daddr;
+
+	daddr.a4.addr = v4daddr;
+	daddr.a4.vif = vif;
+	daddr.family = AF_INET;
+	return inet_getpeer(base, &daddr);
+}
+
+static inline struct inet_peer *inet_getpeer_v6(struct inet_peer_base *base,
+						const struct in6_addr *v6daddr)
+{
+	struct inetpeer_addr daddr;
+
+	daddr.a6 = *v6daddr;
+	daddr.family = AF_INET6;
+	return inet_getpeer(base, &daddr);
+}
+
+static inline int inetpeer_addr_cmp(const struct inetpeer_addr *a,
+				    const struct inetpeer_addr *b)
+{
+	int i, n;
+
+	if (a->family != b->family)
+		return a->family < b->family ? -1 : 1;
+
+	if (a->family == AF_INET)
+		n = sizeof(a->a4) / sizeof(u32);
+	else
+		n = sizeof(a->a6) / sizeof(u32);
+
+	for (i = 0; i < n; i++) {
+		if (a->key[i] == b->key[i])
+			continue;
+		if (a->key[i] < b->key[i])
+			return -1;
+		return 1;
+	}
+
+	return 0;
+}
+
+/* can be called from BH context or outside */
+void inet_putpeer(struct inet_peer *p);
+bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout);
+
+void inetpeer_invalidate_tree(struct inet_peer_base *);
+
+#endif /* _NET_INETPEER_H */