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, 66 insertions, 0 deletions

diff --git a/scripts/cc-version.sh b/scripts/cc-version.sh
new file mode 100755
index 000000000..a7e28b6a5
--- /dev/null
+++ b/scripts/cc-version.sh
@@ -0,0 +1,66 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Print the C compiler name and its version in a 5 or 6-digit form.
+# Also, perform the minimum version check.
+
+set -e
+
+# Print the C compiler name and some version components.
+get_c_compiler_info()
+{
+	cat <<- EOF | "$@" -E -P -x c - 2>/dev/null
+	#if defined(__clang__)
+	Clang	__clang_major__  __clang_minor__  __clang_patchlevel__
+	#elif defined(__GNUC__)
+	GCC	__GNUC__  __GNUC_MINOR__  __GNUC_PATCHLEVEL__
+	#else
+	unknown
+	#endif
+	EOF
+}
+
+# Convert the version string x.y.z to a canonical 5 or 6-digit form.
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+	echo $((10000 * $1 + 100 * $2 + $3))
+}
+
+# $@ instead of $1 because multiple words might be given, e.g. CC="ccache gcc".
+orig_args="$@"
+set -- $(get_c_compiler_info "$@")
+
+name=$1
+
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
+case "$name" in
+GCC)
+	version=$2.$3.$4
+	min_version=$($min_tool_version gcc)
+	;;
+Clang)
+	version=$2.$3.$4
+	min_version=$($min_tool_version llvm)
+	;;
+*)
+	echo "$orig_args: unknown C compiler" >&2
+	exit 1
+	;;
+esac
+
+cversion=$(get_canonical_version $version)
+min_cversion=$(get_canonical_version $min_version)
+
+if [ "$cversion" -lt "$min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** C compiler is too old."
+	echo >&2 "***   Your $name version:    $version"
+	echo >&2 "***   Minimum $name version: $min_version"
+	echo >&2 "***"
+	exit 1
+fi
+
+echo $name $cversion