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, 24 insertions, 0 deletions

diff --git a/tools/testing/shared/maple-shared.h b/tools/testing/shared/maple-shared.h
new file mode 100644
index 000000000..2a1e9a859
--- /dev/null
+++ b/tools/testing/shared/maple-shared.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+#ifndef __MAPLE_SHARED_H__
+#define __MAPLE_SHARED_H__
+
+#define CONFIG_DEBUG_MAPLE_TREE
+#define CONFIG_MAPLE_SEARCH
+#define MAPLE_32BIT (MAPLE_NODE_SLOTS > 31)
+#include "shared.h"
+#include <stdlib.h>
+#include <time.h>
+#include "linux/init.h"
+
+void maple_rcu_cb(struct rcu_head *head);
+#define rcu_cb		maple_rcu_cb
+
+#define kfree_rcu(_struct, _memb)		\
+do {                                            \
+    typeof(_struct) _p_struct = (_struct);      \
+                                                \
+    call_rcu(&((_p_struct)->_memb), rcu_cb);    \
+} while(0);
+
+
+#endif /* __MAPLE_SHARED_H__ */