linux-kernel - [PATCH 3.16 254/294] hostap: avoid uninitialized variable use in hfa384x_get

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Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Arnd Bergmann" <arnd@...db.de>,
        "Kalle Valo" <kvalo@...eaurora.org>
Subject: [PATCH 3.16 254/294] hostap: avoid uninitialized variable use in
 hfa384x_get_rid

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

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

From: Arnd Bergmann <arnd@...db.de>

commit 48dc5fb3ba53b20418de8514700f63d88c5de3a3 upstream.

The driver reads a value from hfa384x_from_bap(), which may fail,
and then assigns the value to a local variable. gcc detects that
in in the failure case, the 'rlen' variable now contains
uninitialized data:

In file included from ../drivers/net/wireless/intersil/hostap/hostap_pci.c:220:0:
drivers/net/wireless/intersil/hostap/hostap_hw.c: In function 'hfa384x_get_rid':
drivers/net/wireless/intersil/hostap/hostap_hw.c:842:5: warning: 'rec' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if (le16_to_cpu(rec.len) == 0) {

This restructures the function as suggested by Russell King, to
make it more readable and get more reliable error handling, by
handling each failure mode using a goto.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/wireless/hostap/hostap_hw.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

--- a/drivers/net/wireless/hostap/hostap_hw.c
+++ b/drivers/net/wireless/hostap/hostap_hw.c
@@ -836,25 +836,30 @@ static int hfa384x_get_rid(struct net_de
 	spin_lock_bh(&local->baplock);
 
 	res = hfa384x_setup_bap(dev, BAP0, rid, 0);
-	if (!res)
-		res = hfa384x_from_bap(dev, BAP0, &rec, sizeof(rec));
+	if (res)
+		goto unlock;
+
+	res = hfa384x_from_bap(dev, BAP0, &rec, sizeof(rec));
+	if (res)
+		goto unlock;
 
 	if (le16_to_cpu(rec.len) == 0) {
 		/* RID not available */
 		res = -ENODATA;
+		goto unlock;
 	}
 
 	rlen = (le16_to_cpu(rec.len) - 1) * 2;
-	if (!res && exact_len && rlen != len) {
+	if (exact_len && rlen != len) {
 		printk(KERN_DEBUG "%s: hfa384x_get_rid - RID len mismatch: "
 		       "rid=0x%04x, len=%d (expected %d)\n",
 		       dev->name, rid, rlen, len);
 		res = -ENODATA;
 	}
 
-	if (!res)
-		res = hfa384x_from_bap(dev, BAP0, buf, len);
+	res = hfa384x_from_bap(dev, BAP0, buf, len);
 
+unlock:
 	spin_unlock_bh(&local->baplock);
 	mutex_unlock(&local->rid_bap_mtx);