From patchwork Thu Feb 13 00:02:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Gustavo A. R. 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R. Silva" To: Matthew Wilcox , Hannes Reinecke , "James E.J. Bottomley" , "Martin K. Petersen" Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH] scsi: advansys: Replace zero-length array with flexible-array member Message-ID: <20200213000211.GA23171@embeddedor.com> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 200.68.141.42 X-Source-L: No X-Exim-ID: 1j21xN-003P9t-Ih X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [200.68.141.42]:17871 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 5 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Reviewed-by: Hannes Reinecke --- drivers/scsi/advansys.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/scsi/advansys.c b/drivers/scsi/advansys.c index a242a62caaa1..c2c7850ff7b4 100644 --- a/drivers/scsi/advansys.c +++ b/drivers/scsi/advansys.c @@ -316,7 +316,7 @@ typedef struct asc_sg_head { ushort queue_cnt; ushort entry_to_copy; ushort res; - ASC_SG_LIST sg_list[0]; + ASC_SG_LIST sg_list[]; } ASC_SG_HEAD; typedef struct asc_scsi_q {