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, 54 insertions, 0 deletions

diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
new file mode 100644
index 000000000..dec7522b6
--- /dev/null
+++ b/include/net/netprio_cgroup.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * netprio_cgroup.h			Control Group Priority set
+ *
+ * Authors:	Neil Horman <nhorman@tuxdriver.com>
+ */
+
+#ifndef _NETPRIO_CGROUP_H
+#define _NETPRIO_CGROUP_H
+
+#include <linux/cgroup.h>
+#include <linux/hardirq.h>
+#include <linux/rcupdate.h>
+
+#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
+struct netprio_map {
+	struct rcu_head rcu;
+	u32 priomap_len;
+	u32 priomap[];
+};
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	struct cgroup_subsys_state *css;
+	u32 idx;
+
+	rcu_read_lock();
+	css = task_css(p, net_prio_cgrp_id);
+	idx = css->id;
+	rcu_read_unlock();
+	return idx;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+	if (in_interrupt())
+		return;
+
+	sock_cgroup_set_prioidx(skcd, task_netprioidx(current));
+}
+
+#else /* !CONFIG_CGROUP_NET_PRIO */
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	return 0;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+}
+
+#endif /* CONFIG_CGROUP_NET_PRIO */
+#endif  /* _NET_CLS_CGROUP_H */