linux-hardening - [PATCH] module: Annotate struct module_notes_attrs with __counted

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Date: Fri, 22 Sep 2023 10:52:53 -0700
From: Kees Cook <keescook@...omium.org>
To: Luis Chamberlain <mcgrof@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
	linux-modules@...r.kernel.org,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Tom Rix <trix@...hat.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: [PATCH] module: Annotate struct module_notes_attrs 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).

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

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

Cc: Luis Chamberlain <mcgrof@...nel.org>
Cc: linux-modules@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/module/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/module/sysfs.c b/kernel/module/sysfs.c
index c921bf044050..d964167c6658 100644
--- a/kernel/module/sysfs.c
+++ b/kernel/module/sysfs.c
@@ -143,7 +143,7 @@ static void remove_sect_attrs(struct module *mod)
 struct module_notes_attrs {
 	struct kobject *dir;
 	unsigned int notes;
-	struct bin_attribute attrs[];
+	struct bin_attribute attrs[] __counted_by(notes);
 };
 
 static ssize_t module_notes_read(struct file *filp, struct kobject *kobj,
-- 
2.34.1