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, 18 insertions, 0 deletions

diff --git a/lib/vdso/Makefile.include b/lib/vdso/Makefile.include
new file mode 100644
index 000000000..cedbf15f8
--- /dev/null
+++ b/lib/vdso/Makefile.include
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0
+
+GENERIC_VDSO_MK_PATH := $(abspath $(lastword $(MAKEFILE_LIST)))
+GENERIC_VDSO_DIR := $(dir $(GENERIC_VDSO_MK_PATH))
+
+c-gettimeofday-$(CONFIG_GENERIC_GETTIMEOFDAY) := $(addprefix $(GENERIC_VDSO_DIR), gettimeofday.c)
+c-getrandom-$(CONFIG_VDSO_GETRANDOM) := $(addprefix $(GENERIC_VDSO_DIR), getrandom.c)
+
+# This cmd checks that the vdso library does not contain dynamic relocations.
+# It has to be called after the linking of the vdso library and requires it
+# as a parameter.
+#
+# As a workaround for some GNU ld ports which produce unneeded R_*_NONE
+# dynamic relocations, ignore R_*_NONE.
+quiet_cmd_vdso_check = VDSOCHK $@
+      cmd_vdso_check = if $(READELF) -rW $@ | grep -v _NONE | grep -q " R_\w*_"; \
+		       then (echo >&2 "$@: dynamic relocations are not supported"; \
+			     rm -f $@; /bin/false); fi