linux-hardening - [PATCH][next] cifs: Replace zero-length arrays with flexible-array members

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Message-ID: <Y7zBtCZ/eRJCpjBf@work>
Date:   Mon, 9 Jan 2023 19:39:00 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Steve French <sfrench@...ba.org>, Paulo Alcantara <pc@....nz>,
        Ronnie Sahlberg <lsahlber@...hat.com>,
        Shyam Prasad N <sprasad@...rosoft.com>,
        Tom Talpey <tom@...pey.com>
Cc:     linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] cifs: Replace zero-length arrays with flexible-array
 members

Zero-length arrays are deprecated[1] and we are moving towards
adopting C99 flexible-array members instead. So, replace zero-length
arrays in a couple of structures with flex-array members.

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>
---
 fs/cifs/ntlmssp.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/ntlmssp.h b/fs/cifs/ntlmssp.h
index 55758b9ec877..2c5dde2ece58 100644
--- a/fs/cifs/ntlmssp.h
+++ b/fs/cifs/ntlmssp.h
@@ -83,7 +83,7 @@ typedef struct _NEGOTIATE_MESSAGE {
 	SECURITY_BUFFER WorkstationName;	/* RFC 1001 and ASCII */
 	/* SECURITY_BUFFER for version info not present since we
 	   do not set the version is present flag */
-	char DomainString[0];
+	char DomainString[];
 	/* followed by WorkstationString */
 } __attribute__((packed)) NEGOTIATE_MESSAGE, *PNEGOTIATE_MESSAGE;
 
@@ -135,7 +135,7 @@ typedef struct _AUTHENTICATE_MESSAGE {
 	__le32 NegotiateFlags;
 	/* SECURITY_BUFFER for version info not present since we
 	   do not set the version is present flag */
-	char UserString[0];
+	char UserString[];
 } __attribute__((packed)) AUTHENTICATE_MESSAGE, *PAUTHENTICATE_MESSAGE;
 
 /*
-- 
2.34.1