linux-kernel - [PATCH v2 1/2] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <1512713739-15838-2-git-send-email-jiada_wang@mentor.com>
Date:   Thu, 7 Dec 2017 22:15:38 -0800
From:   <jiada_wang@...tor.com>
To:     <lgirdwood@...il.com>, <broonie@...nel.org>, <perex@...ex.cz>,
        <tiwai@...e.com>, <kuninori.morimoto.gx@...esas.com>
CC:     <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        Jiada Wang <jiada_wang@...tor.com>
Subject: [PATCH v2 1/2] ASoC: rsnd: ssi: fix race condition in rsnd_ssi_pointer_update

From: Jiada Wang <jiada_wang@...tor.com>

Currently there is race condition between set of byte_pos and wrap
it around when new buffer starts. If .pointer is called in-between
it will result in inconsistent pointer position be returned
from .pointer callback.

This patch increments buffer pointer atomically to avoid this issue.

Signed-off-by: Jiada Wang <jiada_wang@...tor.com>
Reviewed-by: Takashi Sakamoto <takashi.sakamoto@...aclelinux.com>
---
 sound/soc/sh/rcar/ssi.c |   16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/sound/soc/sh/rcar/ssi.c b/sound/soc/sh/rcar/ssi.c
index fece1e5f..cbf3bf3 100644
--- a/sound/soc/sh/rcar/ssi.c
+++ b/sound/soc/sh/rcar/ssi.c
@@ -446,25 +446,29 @@ static bool rsnd_ssi_pointer_update(struct rsnd_mod *mod,
 				    int byte)
 {
 	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
+	bool ret = false;
+	int byte_pos;
 
-	ssi->byte_pos += byte;
+	byte_pos = ssi->byte_pos + byte;
 
-	if (ssi->byte_pos >= ssi->next_period_byte) {
+	if (byte_pos >= ssi->next_period_byte) {
 		struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
 		ssi->period_pos++;
 		ssi->next_period_byte += ssi->byte_per_period;
 
 		if (ssi->period_pos >= runtime->periods) {
-			ssi->byte_pos = 0;
+			byte_pos = 0;
 			ssi->period_pos = 0;
 			ssi->next_period_byte = ssi->byte_per_period;
 		}
 
-		return true;
+		ret = true;
 	}
 
-	return false;
+	WRITE_ONCE(ssi->byte_pos, byte_pos);
+
+	return ret;
 }
 
 /*
@@ -838,7 +842,7 @@ static int rsnd_ssi_pointer(struct rsnd_mod *mod,
 	struct rsnd_ssi *ssi = rsnd_mod_to_ssi(mod);
 	struct snd_pcm_runtime *runtime = rsnd_io_to_runtime(io);
 
-	*pointer = bytes_to_frames(runtime, ssi->byte_pos);
+	*pointer = bytes_to_frames(runtime, READ_ONCE(ssi->byte_pos));
 
 	return 0;
 }
-- 
1.7.9.5