All of lore.kernel.org
 help / color / mirror / Atom feed
From: Arnd Bergmann <arnd@kernel.org>
To: Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
	Wolfgang Grandegger <wg@grandegger.com>,
	Marc Kleine-Budde <mkl@pengutronix.de>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Arunachalam Santhanam <arunachalam.santhanam@in.bosch.com>,
	linux-can@vger.kernel.org, netdev@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH] can: etas_es58x: avoid -Wzero-length-bounds warning
Date: Mon, 20 Sep 2021 14:30:29 +0200	[thread overview]
Message-ID: <20210920123045.795228-1-arnd@kernel.org> (raw)

From: Arnd Bergmann <arnd@arndb.de>

gcc complains when writing into a zero-length array:

drivers/net/can/usb/etas_es58x/es581_4.c: In function 'es581_4_tx_can_msg':
drivers/net/can/usb/etas_es58x/es581_4.c:374:42: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[]'} [-Wzero-length-bounds]
  374 |         tx_can_msg = (typeof(tx_can_msg))&es581_4_urb_cmd->raw_msg[msg_len];
      |                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/net/can/usb/etas_es58x/es58x_core.h:21,
                 from drivers/net/can/usb/etas_es58x/es581_4.c:15:
drivers/net/can/usb/etas_es58x/es581_4.h:195:20: note: while referencing 'raw_msg'
  195 |                 u8 raw_msg[0];
      |                    ^~~~~~~
  CC [M]  drivers/net/can/usb/etas_es58x/es58x_fd.o
drivers/net/can/usb/etas_es58x/es58x_fd.c: In function 'es58x_fd_tx_can_msg':
drivers/net/can/usb/etas_es58x/es58x_fd.c:360:42: warning: array subscript 65535 is outside the bounds of an interior zero-length array 'u8[0]' {aka 'unsigned char[]'} [-Wzero-length-bounds]
  360 |         tx_can_msg = (typeof(tx_can_msg))&es58x_fd_urb_cmd->raw_msg[msg_len];
      |                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from drivers/net/can/usb/etas_es58x/es58x_core.h:22,
                 from drivers/net/can/usb/etas_es58x/es58x_fd.c:17:
drivers/net/can/usb/etas_es58x/es58x_fd.h:222:20: note: while referencing 'raw_msg'
  222 |                 u8 raw_msg[0];
      |                    ^~~~~~~

The solution is usually to use a flexible-array member the struct, but
we can't directly have that inside of a union, nor can it be the only
member of a struct, so add a dummy struct with another zero-length
member to get the intended behavior.

If someone has a better workaround, let me know and I can send a new
patch, as this version is rather ugly.

Fixes: f4f5247daa45 ("can: etas_es58x: rewrite the message cast in es58{1,_fd}_tx_can_msg to increase readability")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/net/can/usb/etas_es58x/es581_4.h  | 5 ++++-
 drivers/net/can/usb/etas_es58x/es58x_fd.h | 5 ++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/net/can/usb/etas_es58x/es581_4.h b/drivers/net/can/usb/etas_es58x/es581_4.h
index 4bc60a6df697..ac5ef88db565 100644
--- a/drivers/net/can/usb/etas_es58x/es581_4.h
+++ b/drivers/net/can/usb/etas_es58x/es581_4.h
@@ -192,7 +192,10 @@ struct es581_4_urb_cmd {
 		struct es581_4_rx_cmd_ret rx_cmd_ret;
 		__le64 timestamp;
 		u8 rx_cmd_ret_u8;
-		u8 raw_msg[0];
+		struct {
+			u8 __pad[0];
+			u8 raw_msg[];
+		};
 	} __packed;
 
 	__le16 reserved_for_crc16_do_not_use;
diff --git a/drivers/net/can/usb/etas_es58x/es58x_fd.h b/drivers/net/can/usb/etas_es58x/es58x_fd.h
index a191891b8777..253e7bafd0b6 100644
--- a/drivers/net/can/usb/etas_es58x/es58x_fd.h
+++ b/drivers/net/can/usb/etas_es58x/es58x_fd.h
@@ -219,7 +219,10 @@ struct es58x_fd_urb_cmd {
 		struct es58x_fd_tx_ack_msg tx_ack_msg;
 		__le64 timestamp;
 		__le32 rx_cmd_ret_le32;
-		u8 raw_msg[0];
+		struct {
+			u8 __pad[0];
+			u8 raw_msg[];
+		};
 	} __packed;
 
 	__le16 reserved_for_crc16_do_not_use;
-- 
2.29.2


             reply	other threads:[~2021-09-20 12:30 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-20 12:30 Arnd Bergmann [this message]
2021-09-21  2:53 ` [PATCH] can: etas_es58x: avoid -Wzero-length-bounds warning Vincent MAILHOL

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210920123045.795228-1-arnd@kernel.org \
    --to=arnd@kernel.org \
    --cc=arnd@arndb.de \
    --cc=arunachalam.santhanam@in.bosch.com \
    --cc=davem@davemloft.net \
    --cc=kuba@kernel.org \
    --cc=linux-can@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mailhol.vincent@wanadoo.fr \
    --cc=mkl@pengutronix.de \
    --cc=netdev@vger.kernel.org \
    --cc=wg@grandegger.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.