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, 37 insertions, 0 deletions

diff --git a/tools/docs/check-variable-fonts.py b/tools/docs/check-variable-fonts.py
new file mode 100755
index 000000000..958d5a745
--- /dev/null
+++ b/tools/docs/check-variable-fonts.py
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0-only
+# Copyright (C) Akira Yokosawa, 2024
+#
+# Ported to Python by (c) Mauro Carvalho Chehab, 2025
+#
+# pylint: disable=C0103
+
+"""
+Detect problematic Noto CJK variable fonts.
+
+or more details, see .../tools/lib/python/kdoc/latex_fonts.py.
+"""
+
+import argparse
+import sys
+import os.path
+
+src_dir = os.path.dirname(os.path.realpath(__file__))
+sys.path.insert(0, os.path.join(src_dir, '../lib/python'))
+
+from kdoc.latex_fonts import LatexFontChecker
+
+checker = LatexFontChecker()
+
+parser=argparse.ArgumentParser(description=checker.description(),
+                               formatter_class=argparse.RawTextHelpFormatter)
+parser.add_argument("--deny-vf",
+                    help="XDG_CONFIG_HOME dir containing fontconfig/fonts.conf file")
+
+args=parser.parse_args()
+
+msg = LatexFontChecker(args.deny_vf).check()
+if msg:
+    print(msg)
+
+sys.exit(1)