linux-hardening - [PATCH] [next] pcmcia: synclink_cs: replace 1-element array with flex-array member

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Message-ID: <Y5mMWEtHWKOiPVU+@mail.google.com>
Date:   Wed, 14 Dec 2022 21:42:00 +1300
From:   Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        Jiri Slaby <jirislaby@...nel.org>,
        Haowen Bai <baihaowen@...zu.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org,
        paulo.miguel.almeida.rodenas@...il.com
Subject: [PATCH] [next] pcmcia: synclink_cs: replace 1-element array with
 flex-array member

One-element arrays are deprecated, and we are replacing them with
flexible array members instead. So, replace one-element array with
flexible-array member in struct RXBUF and refactor the rest of the code
accordingly.

It's worth mentioning that doing a build before/after this patch
results in no binary output differences.

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 [1].

Link: https://github.com/KSPP/linux/issues/79
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836 [1]

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
---
 drivers/char/pcmcia/synclink_cs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index b2735be81ab2..1ab2d552f498 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -105,7 +105,7 @@ static MGSL_PARAMS default_params = {
 typedef struct {
 	int count;
 	unsigned char status;
-	char data[1];
+	char data[];
 } RXBUF;
 
 /* The queue of BH actions to be performed */
@@ -2611,7 +2611,8 @@ static int mgslpc_proc_show(struct seq_file *m, void *v)
 static int rx_alloc_buffers(MGSLPC_INFO *info)
 {
 	/* each buffer has header and data */
-	info->rx_buf_size = sizeof(RXBUF) + info->max_frame_size;
+	info->rx_buf_size = max(offsetof(typeof(RXBUF), data) + 1, sizeof(RXBUF))
+		+ info->max_frame_size;
 
 	/* calculate total allocation size for 8 buffers */
 	info->rx_buf_total_size = info->rx_buf_size * 8;
-- 
2.38.1