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, 27 insertions, 0 deletions

diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
new file mode 100644
index 000000000..b47f4daa4
--- /dev/null
+++ b/scripts/dtc/Makefile
@@ -0,0 +1,27 @@
+# SPDX-License-Identifier: GPL-2.0
+# scripts/dtc makefile
+
+# *** Also keep .gitignore in sync when changing ***
+hostprogs-always-$(CONFIG_DTC)		+= dtc fdtoverlay
+hostprogs-always-$(CHECK_DTBS)		+= dtc
+
+dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \
+		   srcpos.o checks.o util.o
+dtc-objs	+= dtc-lexer.lex.o dtc-parser.tab.o
+
+# The upstream project builds libfdt as a separate library.  We are choosing to
+# instead directly link the libfdt object files into fdtoverlay.
+libfdt-objs	:= fdt.o fdt_ro.o fdt_wip.o fdt_sw.o fdt_rw.o fdt_strerror.o fdt_empty_tree.o fdt_addresses.o fdt_overlay.o
+libfdt		= $(addprefix libfdt/,$(libfdt-objs))
+fdtoverlay-objs	:= $(libfdt) fdtoverlay.o util.o
+
+# Source files need to get at the userspace version of libfdt_env.h to compile
+HOST_EXTRACFLAGS += -I $(src)/libfdt
+HOST_EXTRACFLAGS += -DNO_YAML
+
+# Generated files need one more search path to include headers in source tree
+HOSTCFLAGS_dtc-lexer.lex.o := -I $(src)
+HOSTCFLAGS_dtc-parser.tab.o := -I $(src)
+
+# dependencies on generated files need to be listed explicitly
+$(obj)/dtc-lexer.lex.o: $(obj)/dtc-parser.tab.h