linux-kernel - [PATCH] isdn: isdnloop: fix pointer dereference bug

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Date:   Thu,  7 Mar 2019 10:32:07 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Karsten Keil <isdn@...ux-pingi.de>,
        "David S. Miller" <davem@...emloft.net>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] isdn: isdnloop: fix pointer dereference bug

clang has spotted an ancient code bug and warns about it with:

drivers/isdn/isdnloop/isdnloop.c:573:12: error: address of array 'card->rcard' will always evaluate to 'true' [-Werror,-Wpointer-bool-conversion]

This is an array of pointers, so we should check if a specific
pointer exists in the array before using it, not whether the
array itself exists.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/isdn/isdnloop/isdnloop.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/isdn/isdnloop/isdnloop.c b/drivers/isdn/isdnloop/isdnloop.c
index f4253d468ae1..755c6bbc9553 100644
--- a/drivers/isdn/isdnloop/isdnloop.c
+++ b/drivers/isdn/isdnloop/isdnloop.c
@@ -570,7 +570,7 @@ isdnloop_atimeout(isdnloop_card *card, int ch)
 	char buf[60];
 
 	spin_lock_irqsave(&card->isdnloop_lock, flags);
-	if (card->rcard) {
+	if (card->rcard[ch]) {
 		isdnloop_fake(card->rcard[ch], "DDIS_I", card->rch[ch] + 1);
 		card->rcard[ch]->rcard[card->rch[ch]] = NULL;
 		card->rcard[ch] = NULL;
-- 
2.20.0