wl1251: fix potential crash

commit 3f60ebc9d6291863652d564bacc430629271e6a9 upstream.

In case debugfs does not init for some reason (or is disabled
on older kernels) driver does not allocate stats.fw_stats
structure, but tries to clear it later and trips on a NULL
pointer:

Unable to handle kernel NULL pointer dereference at virtual address
00000000
PC is at __memzero+0x24/0x80
Backtrace:
[<bf0ddb88>] (wl1251_debugfs_reset+0x0/0x30 [wl1251])
[<bf0d6a2c>] (wl1251_op_stop+0x0/0x12c [wl1251])
[<bf0bc228>] (ieee80211_stop_device+0x0/0x74 [mac80211])
[<bf0b0d10>] (ieee80211_stop+0x0/0x4ac [mac80211])
[<c02deeac>] (dev_close+0x0/0xb4)
[<c02deac0>] (dev_change_flags+0x0/0x184)
[<c031f478>] (devinet_ioctl+0x0/0x704)
[<c0320720>] (inet_ioctl+0x0/0x100)

Add a NULL pointer check to fix this.

Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Acked-by: Kalle Valo <kalle.valo@iki.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/net/wireless/wl12xx/wl1251_debugfs.c b/drivers/net/wireless/wl12xx/wl1251_debugfs.c
index a00723059f83..1685c09c8589 100644
--- a/drivers/net/wireless/wl12xx/wl1251_debugfs.c
+++ b/drivers/net/wireless/wl12xx/wl1251_debugfs.c
@@ -443,7 +443,8 @@ out:
 
 void wl1251_debugfs_reset(struct wl1251 *wl)
 {
-        memset(wl->stats.fw_stats, 0, sizeof(*wl->stats.fw_stats));
+        if (wl->stats.fw_stats != NULL)
+                memset(wl->stats.fw_stats, 0, sizeof(*wl->stats.fw_stats));
         wl->stats.retry_count = 0;
         wl->stats.excessive_retries = 0;
 }