[PATCH] kexec: Annotate struct crash_mem with __counted_by

[Kees Cook]

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct crash_mem.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: kexec@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 include/linux/crash_core.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index 3426f6eef60b..5126a4fecb44 100644
--- a/include/linux/crash_core.h
+++ b/include/linux/crash_core.h
@@ -131,7 +131,7 @@ static inline void __init reserve_crashkernel_generic(char *cmdline,
 struct crash_mem {
 	unsigned int max_nr_ranges;
 	unsigned int nr_ranges;
-	struct range ranges[];
+	struct range ranges[] __counted_by(max_nr_ranges);
 };
 
 extern int crash_exclude_mem_range(struct crash_mem *mem,
-- 
2.34.1