x86/platform/uv: Annotate struct uv_rtc_timer_head with __counted_by

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).

Found with Coccinelle:

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

Add __counted_by for struct uv_rtc_timer_head.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230922175151.work.118-kees@kernel.org

diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
index 54663f3e00cbd8ee2b53438f00f429fc57e9c83f..ff5afc8a5a41ea4e379f409e4803af2e4fedef26 100644 (file)
--- a/arch/x86/platform/uv/uv_time.c
+++ b/arch/x86/platform/uv/uv_time.c
@@ -53,7 +53,7 @@ struct uv_rtc_timer_head {
        struct {
                int     lcpu;           /* systemwide logical cpu number */
                u64     expires;        /* next timer expiration for this cpu */
-       } cpu[];
+       } cpu[] __counted_by(ncpus);
 };
 
 /*