lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Thu, 7 May 2020 10:17:58 -0500
From:   "Gustavo A. R. Silva" <>
To:     Kalle Valo <>,
        "David S. Miller" <>,
        Maxime Coquelin <>,
        Alexandre Torgue <>
        "Gustavo A. R. Silva" <>
Subject: [PATCH] wcn36xx: Replace zero-length array with flexible-array

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]

sizeof(flexible-array-member) triggers a warning because flexible array
members have incomplete type[1]. There are some instances of code in
which the sizeof operator is being incorrectly/erroneously applied to
zero-length arrays and the result is zero. Such instances may be hiding
some bugs. So, this work (flexible-array member conversions) will also
help to get completely rid of those sorts of issues.

This issue was found with the help of Coccinelle.

[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <>
 drivers/net/wireless/ath/wcn36xx/hal.h      | 4 ++--
 drivers/net/wireless/ath/wcn36xx/testmode.h | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/ath/wcn36xx/hal.h b/drivers/net/wireless/ath/wcn36xx/hal.h
index 6ba0fd57c951..aab5a58616fc 100644
--- a/drivers/net/wireless/ath/wcn36xx/hal.h
+++ b/drivers/net/wireless/ath/wcn36xx/hal.h
@@ -2240,7 +2240,7 @@ struct wcn36xx_hal_process_ptt_msg_req_msg {
 	struct wcn36xx_hal_msg_header header;
 	/* Actual FTM Command body */
-	u8 ptt_msg[0];
+	u8 ptt_msg[];
 } __packed;
 struct wcn36xx_hal_process_ptt_msg_rsp_msg {
@@ -2249,7 +2249,7 @@ struct wcn36xx_hal_process_ptt_msg_rsp_msg {
 	/* FTM Command response status */
 	u32 ptt_msg_resp_status;
 	/* Actual FTM Command body */
-	u8 ptt_msg[0];
+	u8 ptt_msg[];
 } __packed;
 struct update_edca_params_req_msg {
diff --git a/drivers/net/wireless/ath/wcn36xx/testmode.h b/drivers/net/wireless/ath/wcn36xx/testmode.h
index 4c6cfdb46580..09d68fab9add 100644
--- a/drivers/net/wireless/ath/wcn36xx/testmode.h
+++ b/drivers/net/wireless/ath/wcn36xx/testmode.h
@@ -20,7 +20,7 @@ struct ftm_rsp_msg {
 	u16 msg_id;
 	u16 msg_body_length;
 	u32 resp_status;
-	u8 msg_response[0];
+	u8 msg_response[];
 } __packed;
 /* The request buffer of FTM which contains a byte of command and the request */

Powered by blists - more mailing lists