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.userprogs b/scripts/Makefile.userprogs
new file mode 100644
index 000000000..f3a7e1ef3
--- /dev/null
+++ b/scripts/Makefile.userprogs
@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Build userspace programs for the target system
+#
+
+# Executables compiled from a single .c file
+user-csingle	:= $(foreach m, $(userprogs), $(if $($(m)-objs),,$(m)))
+
+# Executables linked based on several .o files
+user-cmulti	:= $(foreach m, $(userprogs), $(if $($(m)-objs),$(m)))
+
+# Objects compiled from .c files
+user-cobjs	:= $(sort $(foreach m, $(userprogs), $($(m)-objs)))
+
+user-csingle	:= $(addprefix $(obj)/, $(user-csingle))
+user-cmulti	:= $(addprefix $(obj)/, $(user-cmulti))
+user-cobjs	:= $(addprefix $(obj)/, $(user-cobjs))
+
+user_ccflags	= -Wp,-MMD,$(depfile) $(KBUILD_USERCFLAGS) $(userccflags) \
+			$($(target-stem)-userccflags)
+user_ldflags	= $(KBUILD_USERLDFLAGS) $(userldflags) $($(target-stem)-userldflags)
+user_ldlibs	= $(userldlibs) $($(target-stem)-userldlibs)
+
+# Create an executable from a single .c file
+quiet_cmd_user_cc_c = CC [U]  $@
+      cmd_user_cc_c = $(CC) $(user_ccflags) $(user_ldflags) -o $@ $< \
+		      $(user_ldlibs)
+$(user-csingle): $(obj)/%: $(src)/%.c FORCE
+	$(call if_changed_dep,user_cc_c)
+
+# Link an executable based on list of .o files
+quiet_cmd_user_ld = LD [U]  $@
+      cmd_user_ld = $(CC) $(user_ldflags) -o $@ \
+		    $(addprefix $(obj)/, $($(target-stem)-objs)) $(user_ldlibs)
+$(user-cmulti): FORCE
+	$(call if_changed,user_ld)
+$(call multi_depend, $(user-cmulti), , -objs)
+
+# Create .o file from a .c file
+quiet_cmd_user_cc_o_c = CC [U]  $@
+      cmd_user_cc_o_c = $(CC) $(user_ccflags) -c -o $@ $<
+$(user-cobjs): $(obj)/%.o: $(src)/%.c FORCE
+	$(call if_changed_dep,user_cc_o_c)
+
+targets += $(user-csingle) $(user-cmulti) $(user-cobjs)