linux-kernel - [PATCH] ASoC: soc-dapm: Fix comparison of pointers

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Message-Id: <1418162021-32229-1-git-send-email-linux@rasmusvillemoes.dk>
Date:	Tue,  9 Dec 2014 22:53:41 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Mark Brown <broonie@...nel.org>, Takashi Iwai <tiwai@...e.de>
Cc:	Rasmus Villemoes <linux@...musvillemoes.dk>,
	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: [PATCH] ASoC: soc-dapm: Fix comparison of pointers

The idiom 'return a - b;' often used in comparison functions is wrong
unless one is certain the values being compared lie in a sufficiently
small range. In this case dapm_seq_compare would also return 0 if the
->dapm pointers happened to differ by a multiple of 2^32.

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---

Notes:
    I don't know if the other occurences of the idiom in this function are
    ok; that depends on whether the values always lie in [0, 2^31-1].

 sound/soc/soc-dapm.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index c61cb9cedbcd..a894a7c71557 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1255,8 +1255,10 @@ static int dapm_seq_compare(struct snd_soc_dapm_widget *a,
 	}
 	if (a->reg != b->reg)
 		return a->reg - b->reg;
-	if (a->dapm != b->dapm)
-		return (unsigned long)a->dapm - (unsigned long)b->dapm;
+	if (a->dapm < b->dapm)
+		return -1;
+	if (a->dapm > b->dapm)
+		return 1;
 
 	return 0;
 }
-- 
2.1.3

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