linux-kernel - [PATCH] mm/memcg: Annotate struct mem_cgroup_threshold_ary with __counted

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Message-Id: <20230922175327.work.985-kees@kernel.org>
Date:   Fri, 22 Sep 2023 10:53:28 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Shakeel Butt <shakeelb@...gle.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...e.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, Yosry Ahmed <yosryahmed@...gle.com>,
        Yu Zhao <yuzhao@...gle.com>, Miaohe Lin <linmiaohe@...wei.com>,
        Yafang Shao <laoar.shao@...il.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: [PATCH] mm/memcg: Annotate struct mem_cgroup_threshold_ary 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 mem_cgroup_threshold_ary.

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

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Shakeel Butt <shakeelb@...gle.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 include/linux/memcontrol.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 45d0c10e86cc..e0cfab58ab71 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -143,7 +143,7 @@ struct mem_cgroup_threshold_ary {
 	/* Size of entries[] */
 	unsigned int size;
 	/* Array of thresholds */
-	struct mem_cgroup_threshold entries[];
+	struct mem_cgroup_threshold entries[] __counted_by(size);
 };
 
 struct mem_cgroup_thresholds {
-- 
2.34.1