linux-kernel - [PATCH v2 1/2] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config

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Message-ID: <20241007222301.24154-1-alpernebiyasak@gmail.com>
Date: Tue,  8 Oct 2024 01:20:54 +0300
From: Alper Nebi Yasak <alpernebiyasak@...il.com>
To: linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Francesco Dolcini <francesco@...cini.it>,
	Johannes Berg <johannes.berg@...el.com>,
	Kees Cook <kees@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Dmitry Antipov <dmantipov@...dex.ru>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	Brian Norris <briannorris@...omium.org>,
	David Lin <yu-hao.lin@....com>,
	linux-hardening@...r.kernel.org,
	Kalle Valo <kvalo@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Alper Nebi Yasak <alpernebiyasak@...il.com>
Subject: [PATCH v2 1/2] wifi: mwifiex: Fix memcpy() field-spanning write warning in mwifiex_config_scan()

Replace one-element array with a flexible-array member in `struct
mwifiex_ie_types_wildcard_ssid_params` to fix the following warning
on a MT8173 Chromebook (mt8173-elm-hana):

[  356.775250] ------------[ cut here ]------------
[  356.784543] memcpy: detected field-spanning write (size 6) of single field "wildcard_ssid_tlv->ssid" at drivers/net/wireless/marvell/mwifiex/scan.c:904 (size 1)
[  356.813403] WARNING: CPU: 3 PID: 742 at drivers/net/wireless/marvell/mwifiex/scan.c:904 mwifiex_scan_networks+0x4fc/0xf28 [mwifiex]

The "(size 6)" above is exactly the length of the SSID of the network
this device was connected to. The source of the warning looks like:

    ssid_len = user_scan_in->ssid_list[i].ssid_len;
    [...]
    memcpy(wildcard_ssid_tlv->ssid,
           user_scan_in->ssid_list[i].ssid, ssid_len);

There is a #define WILDCARD_SSID_TLV_MAX_SIZE that uses sizeof() on this
struct, but it already didn't account for the size of the one-element
array, so it doesn't need to be changed.

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Signed-off-by: Alper Nebi Yasak <alpernebiyasak@...il.com>
---

Changes in v2:
- Drop unnecessary +1 from scan.c #define WILDCARD_SSID_TLV_MAX_SIZE

v1: https://lore.kernel.org/lkml/20240917150938.843879-1-alpernebiyasak@gmail.com/

 drivers/net/wireless/marvell/mwifiex/fw.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/marvell/mwifiex/fw.h b/drivers/net/wireless/marvell/mwifiex/fw.h
index d03129d5d24e..4a96281792cc 100644
--- a/drivers/net/wireless/marvell/mwifiex/fw.h
+++ b/drivers/net/wireless/marvell/mwifiex/fw.h
@@ -875,7 +875,7 @@ struct mwifiex_ietypes_chanstats {
 struct mwifiex_ie_types_wildcard_ssid_params {
 	struct mwifiex_ie_types_header header;
 	u8 max_ssid_length;
-	u8 ssid[1];
+	u8 ssid[];
 } __packed;
 
 #define TSF_DATA_SIZE            8

base-commit: 58ca61c1a866bfdaa5e19fb19a2416764f847d75
-- 
2.45.2