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, 45 insertions, 0 deletions

diff --git a/scripts/Makefile.vdsoinst b/scripts/Makefile.vdsoinst
new file mode 100644
index 000000000..d9f724321
--- /dev/null
+++ b/scripts/Makefile.vdsoinst
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# ==========================================================================
+# Install unstripped copies of vDSO
+# ==========================================================================
+
+PHONY := __default
+__default:
+	@:
+
+include $(srctree)/scripts/Kbuild.include
+
+install-dir := $(MODLIB)/vdso
+
+define gen_install_rules
+
+dest := $(install-dir)/$$(patsubst %.dbg,%,$$(notdir $(1)))
+
+__default: $$(dest)
+$$(dest): $(1) FORCE
+	$$(call cmd,install)
+
+build-id-file := $$(shell $(READELF) -n $(1) 2>/dev/null | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+
+ifneq ($$(build-id-file),)
+link := $(install-dir)/.build-id/$$(build-id-file).debug
+
+__default: $$(link)
+$$(link): $$(dest) FORCE
+	$$(call cmd,symlink)
+endif
+
+endef
+
+$(foreach x, $(sort $(INSTALL_FILES)), $(eval $(call gen_install_rules,$(x))))
+
+quiet_cmd_install = INSTALL $@
+      cmd_install = mkdir -p $(dir $@); cp $< $@
+
+quiet_cmd_symlink = SYMLINK $@
+      cmd_symlink = mkdir -p $(dir $@); ln -sf --relative $< $@
+
+PHONY += FORCE
+FORCE:
+
+.PHONY: $(PHONY)