linux-hardening - [PATCH] powerpc/rtas: Replace one-element array with flexible array member

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Message-ID: <20250513174003.335857-2-thorsten.blum@linux.dev>
Date: Tue, 13 May 2025 19:40:01 +0200
From: Thorsten Blum <thorsten.blum@...ux.dev>
To: Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Thorsten Blum <thorsten.blum@...ux.dev>,
	linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] powerpc/rtas: Replace one-element array with flexible array member

Replace the deprecated one-element array with a modern flexible array
member in the struct rtas_error_log and add the __counted_by_be()
compiler attribute to improve access bounds-checking via
CONFIG_UBSAN_BOUNDS and CONFIG_FORTIFY_SOURCE.

No functional changes intended.

Link: https://github.com/KSPP/linux/issues/79
Link: https://github.com/KSPP/linux/issues/83
Signed-off-by: Thorsten Blum <thorsten.blum@...ux.dev>
---
 arch/powerpc/include/asm/rtas-types.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/rtas-types.h b/arch/powerpc/include/asm/rtas-types.h
index 9d5b16803cbb..5d40d187b965 100644
--- a/arch/powerpc/include/asm/rtas-types.h
+++ b/arch/powerpc/include/asm/rtas-types.h
@@ -42,8 +42,9 @@ struct rtas_error_log {
 	 */
 	u8		byte3;			/* General event or error*/
 	__be32		extended_log_length;	/* length in bytes */
-	unsigned char	buffer[1];		/* Start of extended log */
-						/* Variable length.      */
+
+	/* Start of extended log, variable length */
+	unsigned char	buffer[] __counted_by_be(extended_log_length);
 };
 
 /* RTAS general extended event log, Version 6. The extended log starts
-- 
2.49.0