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, 84 insertions, 0 deletions

diff --git a/scripts/Makefile.headersinst b/scripts/Makefile.headersinst
new file mode 100644
index 000000000..029d85bb0
--- /dev/null
+++ b/scripts/Makefile.headersinst
@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: GPL-2.0
+# ==========================================================================
+# Installing headers
+#
+# All headers under include/uapi, include/generated/uapi,
+# arch/<arch>/include/uapi and arch/<arch>/include/generated/uapi are
+# exported.
+# They are preprocessed to remove __KERNEL__ section of the file.
+#
+# ==========================================================================
+
+PHONY := __headers
+__headers:
+
+include $(srctree)/scripts/Kbuild.include
+
+src := $(srctree)/$(obj)
+gen := $(objtree)/$(subst include/,include/generated/,$(obj))
+dst := usr/include
+
+-include $(src)/Kbuild
+
+# $(filter %/, ...) is a workaround for GNU Make <= 4.2.1, where
+# $(wildcard $(src)/*/) contains not only directories but also regular files.
+src-subdirs := $(patsubst $(src)/%/,%,$(filter %/, $(wildcard $(src)/*/)))
+gen-subdirs := $(patsubst $(gen)/%/,%,$(filter %/, $(wildcard $(gen)/*/)))
+all-subdirs := $(sort $(src-subdirs) $(gen-subdirs))
+
+src-headers := $(if $(src-subdirs), $(shell cd $(src) && find $(src-subdirs) -name '*.h'))
+src-headers := $(filter-out $(no-export-headers), $(src-headers))
+gen-headers := $(if $(gen-subdirs), $(shell cd $(gen) && find $(gen-subdirs) -name '*.h'))
+gen-headers := $(filter-out $(no-export-headers), $(gen-headers))
+
+# If the same header is exported from source and generated directories,
+# the former takes precedence, but this should be warned.
+duplicated := $(filter $(gen-headers), $(src-headers))
+$(if $(duplicated), $(warning duplicated header export: $(duplicated)))
+
+gen-headers := $(filter-out $(duplicated), $(gen-headers))
+
+# Add dst path prefix
+all-subdirs := $(addprefix $(dst)/, $(all-subdirs))
+src-headers := $(addprefix $(dst)/, $(src-headers))
+gen-headers := $(addprefix $(dst)/, $(gen-headers))
+all-headers := $(src-headers) $(gen-headers)
+
+# Work out what needs to be removed
+old-subdirs := $(wildcard $(all-subdirs))
+old-headers := $(if $(old-subdirs),$(shell find $(old-subdirs) -name '*.h'))
+unwanted    := $(filter-out $(all-headers), $(old-headers))
+
+# Create directories
+existing-dirs := $(sort $(dir $(old-headers)))
+wanted-dirs   := $(sort $(dir $(all-headers)))
+new-dirs      := $(filter-out $(existing-dirs), $(wanted-dirs))
+$(if $(new-dirs), $(shell mkdir -p $(new-dirs)))
+
+# Rules
+quiet_cmd_install = HDRINST $@
+      cmd_install = $(CONFIG_SHELL) $(srctree)/scripts/headers_install.sh $< $@
+
+$(src-headers): $(dst)/%.h: $(src)/%.h $(srctree)/scripts/headers_install.sh FORCE
+	$(call if_changed,install)
+
+$(gen-headers): $(dst)/%.h: $(gen)/%.h $(srctree)/scripts/headers_install.sh FORCE
+	$(call if_changed,install)
+
+quiet_cmd_remove = REMOVE  $(unwanted)
+      cmd_remove = rm -f $(unwanted)
+
+__headers: $(all-headers)
+ifneq ($(unwanted),)
+	$(call cmd,remove)
+endif
+	@:
+
+existing-headers := $(filter $(old-headers), $(all-headers))
+
+-include $(foreach f,$(existing-headers),$(dir $(f)).$(notdir $(f)).cmd)
+
+PHONY += FORCE
+FORCE:
+
+.PHONY: $(PHONY)