linux-kernel - [PATCH 3.16 055/212] mwifiex: debugfs: Fix (sometimes) off-by-1 SSID print

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Message-ID: <lsq.1496331795.692015193@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:43:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Brian Norris" <briannorris@...omium.org>,
        "Kalle Valo" <kvalo@...eaurora.org>
Subject: [PATCH 3.16 055/212] mwifiex: debugfs: Fix (sometimes) off-by-1
 SSID print

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Brian Norris <briannorris@...omium.org>

commit 6183468a23fc6b6903f8597982017ad2c7fdefcf upstream.

Similar to commit fcd2042e8d36 ("mwifiex: printk() overflow with 32-byte
SSIDs"), we failed to account for the existence of 32-char SSIDs in our
debugfs code. Unlike in that case though, we zeroed out the containing
struct first, and I'm pretty sure we're guaranteed to have some padding
after the 'ssid.ssid' and 'ssid.ssid_len' fields (the struct is 33 bytes
long).

So, this is the difference between:

  # cat /sys/kernel/debug/mwifiex/mlan0/info
  ...
  essid="0123456789abcdef0123456789abcdef "
  ...

and the correct output:

  # cat /sys/kernel/debug/mwifiex/mlan0/info
  ...
  essid="0123456789abcdef0123456789abcdef"
  ...

Fixes: 5e6e3a92b9a4 ("wireless: mwifiex: initial commit for Marvell mwifiex driver")
Signed-off-by: Brian Norris <briannorris@...omium.org>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
[bwh: Backported to 3.16: adjsut filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/wireless/mwifiex/debugfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/mwifiex/debugfs.c
+++ b/drivers/net/wireless/mwifiex/debugfs.c
@@ -220,7 +220,8 @@ mwifiex_info_read(struct file *file, cha
 	if (GET_BSS_ROLE(priv) == MWIFIEX_BSS_ROLE_STA) {
 		p += sprintf(p, "multicast_count=\"%d\"\n",
 			     netdev_mc_count(netdev));
-		p += sprintf(p, "essid=\"%s\"\n", info.ssid.ssid);
+		p += sprintf(p, "essid=\"%.*s\"\n", info.ssid.ssid_len,
+			     info.ssid.ssid);
 		p += sprintf(p, "bssid=\"%pM\"\n", info.bssid);
 		p += sprintf(p, "channel=\"%d\"\n", (int) info.bss_chan);
 		p += sprintf(p, "country_code = \"%s\"\n", info.country_code);