linux-kernel - [PATCH v2] lsm: Add a __counted_by() annotation to lsm

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Message-Id: <20231222-lsm-fix-counted-by-v2-1-f1237a095bdc@kernel.org>
Date: Fri, 22 Dec 2023 14:54:37 +0000
From: Mark Brown <broonie@...nel.org>
To: Paul Moore <paul@...l-moore.com>, James Morris <jmorris@...ei.org>, 
 "Serge E. Hallyn" <serge@...lyn.com>, Kees Cook <keescook@...omium.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-hardening@...r.kernel.org, Aishwarya TCV <aishwarya.tcv@....com>, 
 Mark Brown <broonie@...nel.org>
Subject: [PATCH v2] lsm: Add a __counted_by() annotation to lsm_ctx.ctx

The ctx in struct lsm_ctx is an array of size ctx_len, tell the compiler
about this using __counted_by() where supported to improve the ability to
detect overflow issues.

Reported-by: Aishwarya TCV <aishwarya.tcv@....com>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
Changes in v2:
- Add explicit stddef.h inclusion in case __counted_by() definition
  isn't otherwise pulled in.
- Link to v1: https://lore.kernel.org/r/20231221-lsm-fix-counted-by-v1-1-12cc27597cdf@kernel.org
---
 include/uapi/linux/lsm.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h
index f0386880a78e..f8aef9ade549 100644
--- a/include/uapi/linux/lsm.h
+++ b/include/uapi/linux/lsm.h
@@ -9,6 +9,7 @@
 #ifndef _UAPI_LINUX_LSM_H
 #define _UAPI_LINUX_LSM_H

+#include <linux/stddef.h>
 #include <linux/types.h>
 #include <linux/unistd.h>

@@ -36,7 +37,7 @@ struct lsm_ctx {
 	__u64 flags;
 	__u64 len;
 	__u64 ctx_len;
-	__u8 ctx[];
+	__u8 ctx[] __counted_by(ctx_len);
 };

 /*

---
base-commit: ec4e9d630a64df500641892f4e259e8149594a99
change-id: 20231221-lsm-fix-counted-by-f9fd827e26aa

Best regards,
-- 
Mark Brown <broonie@...nel.org>