linux-hardening - [PATCH][next] x86/fpu: Replace zero-length array with flexible-array member

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Date:   Mon, 9 Jan 2023 19:40:38 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] x86/fpu: Replace zero-length array with flexible-array
 member

Zero-length arrays are deprecated[1] and we are moving towards
adopting C99 flexible-array members instead. So, replace zero-length
array declaration in struct xregs_state with flex-array member.

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [2].

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays [1]
Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [2]
Link: https://github.com/KSPP/linux/issues/78
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 arch/x86/include/asm/fpu/types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index eb7cd1139d97..7f6d858ff47a 100644
--- a/arch/x86/include/asm/fpu/types.h
+++ b/arch/x86/include/asm/fpu/types.h
@@ -321,7 +321,7 @@ struct xstate_header {
 struct xregs_state {
 	struct fxregs_state		i387;
 	struct xstate_header		header;
-	u8				extended_state_area[0];
+	u8				extended_state_area[];
 } __attribute__ ((packed, aligned (64)));
 
 /*
-- 
2.34.1