bpf: mark a NULL kfunc argument precisegrafted

check_kfunc_arg() allows bpf_register_is_null() for nullable arguments
w/o marking the underlying scalar register precise. Hence a checkpoint
created on such a path would prune against arbitrary scalar value.

Fixes: 3bda08b63670 ("bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20260904-register-is-null-precise-fixes-v1-5-0f5a360ff15d@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/misc/lkdtm/Makefile b/drivers/misc/lkdtm/Makefile
new file mode 100644
index 000000000..4e58d16fc
--- /dev/null
+++ b/drivers/misc/lkdtm/Makefile
@@ -0,0 +1,25 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_LKDTM)		+= lkdtm.o
+
+lkdtm-$(CONFIG_LKDTM)		+= core.o
+lkdtm-$(CONFIG_LKDTM)		+= bugs.o
+lkdtm-$(CONFIG_LKDTM)		+= heap.o
+lkdtm-$(CONFIG_LKDTM)		+= perms.o
+lkdtm-$(CONFIG_LKDTM)		+= refcount.o
+lkdtm-$(CONFIG_LKDTM)		+= rodata_objcopy.o
+lkdtm-$(CONFIG_LKDTM)		+= usercopy.o
+lkdtm-$(CONFIG_LKDTM)		+= kstack_erase.o
+lkdtm-$(CONFIG_LKDTM)		+= cfi.o
+lkdtm-$(CONFIG_LKDTM)		+= fortify.o
+lkdtm-$(CONFIG_PPC_BOOK3S_64)	+= powerpc.o
+
+KASAN_SANITIZE_stackleak.o	:= n
+
+CFLAGS_REMOVE_rodata.o			+= $(CC_FLAGS_LTO) $(RETHUNK_CFLAGS) $(CC_FLAGS_CFI)
+
+OBJCOPYFLAGS :=
+OBJCOPYFLAGS_rodata_objcopy.o	:= \
+			--rename-section .noinstr.text=.rodata,alloc,readonly,load,contents
+targets += rodata.o rodata_objcopy.o
+$(obj)/rodata_objcopy.o: $(obj)/rodata.o FORCE
+	$(call if_changed,objcopy)