From patchwork Tue Feb 25 01:20:08 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: Luis Chamberlain , Kalle Valo , "David S. Miller" Cc: linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" Subject: [PATCH][next] prism54: Replace zero-length array with flexible-array member Message-ID: <20200225012008.GA4309@embeddedor> 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: 201.166.191.50 X-Source-L: No X-Exim-ID: 1j6Oqd-002v0R-6d X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: (embeddedor) [201.166.191.50]:58608 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 27 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@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 --- drivers/net/wireless/intersil/prism54/isl_oid.h | 8 ++++---- drivers/net/wireless/intersil/prism54/islpci_mgt.h | 2 +- 2 files changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/net/wireless/intersil/prism54/isl_oid.h b/drivers/net/wireless/intersil/prism54/isl_oid.h index 5441c1f9f2fc..1afc2ccf94ca 100644 --- a/drivers/net/wireless/intersil/prism54/isl_oid.h +++ b/drivers/net/wireless/intersil/prism54/isl_oid.h @@ -37,7 +37,7 @@ struct obj_mlmeex { u16 state; u16 code; u16 size; - u8 data[0]; + u8 data[]; } __packed; struct obj_buffer { @@ -68,12 +68,12 @@ struct obj_bss { struct obj_bsslist { u32 nr; - struct obj_bss bsslist[0]; + struct obj_bss bsslist[]; } __packed; struct obj_frequencies { u16 nr; - u16 mhz[0]; + u16 mhz[]; } __packed; struct obj_attachment { @@ -81,7 +81,7 @@ struct obj_attachment { char reserved; short id; short size; - char data[0]; + char data[]; } __packed; /* diff --git a/drivers/net/wireless/intersil/prism54/islpci_mgt.h b/drivers/net/wireless/intersil/prism54/islpci_mgt.h index d6bbbac46b4a..1f87d0aea60c 100644 --- a/drivers/net/wireless/intersil/prism54/islpci_mgt.h +++ b/drivers/net/wireless/intersil/prism54/islpci_mgt.h @@ -99,7 +99,7 @@ struct islpci_mgmtframe { pimfor_header_t *header; /* payload header, points into buf */ void *data; /* payload ex header, points into buf */ struct work_struct ws; /* argument for schedule_work() */ - char buf[0]; /* fragment buffer */ + char buf[]; /* fragment buffer */ }; int