linux-kernel - [PATCH] soc: soc-dapm: fix two incorrect uses of list iterator

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Date:   Sun, 27 Mar 2022 16:21:38 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Xiaomeng Tong <xiam0nd.tong@...il.com>, stable@...r.kernel.org
Subject: [PATCH] soc: soc-dapm: fix two incorrect uses of list iterator

These two bug are here:
	list_for_each_entry_safe_continue(w, n, list,
					power_list);
	list_for_each_entry_safe_continue(w, n, list,
					power_list);

After the list_for_each_entry_safe_continue() exits, the list iterator
will always be a bogus pointer which point to an invalid struct objdect
containing HEAD member. The funciton poniter 'w->event' will be a
invalid value which can lead to a control-flow hijack if the 'w' can be
controlled.

The original intention was to break the outer list_for_each_entry_safe()
loop if w->event is NULL, but forgot to *break* switch statement first.
So just add a break to fix the bug.

Cc: stable@...r.kernel.org
Fixes: 163cac061c973 ("ASoC: Factor out DAPM sequence execution")
Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 sound/soc/soc-dapm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index b06c5682445c..2a5a64d21856 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1686,9 +1686,11 @@ static void dapm_seq_run(struct snd_soc_card *card,
 
 		switch (w->id) {
 		case snd_soc_dapm_pre:
-			if (!w->event)
+			if (!w->event) {
 				list_for_each_entry_safe_continue(w, n, list,
 								  power_list);
+				break;
+			}
 
 			if (event == SND_SOC_DAPM_STREAM_START)
 				ret = w->event(w,
@@ -1699,9 +1701,11 @@ static void dapm_seq_run(struct snd_soc_card *card,
 			break;
 
 		case snd_soc_dapm_post:
-			if (!w->event)
+			if (!w->event) {
 				list_for_each_entry_safe_continue(w, n, list,
 								  power_list);
+				break;
+			}
 
 			if (event == SND_SOC_DAPM_STREAM_START)
 				ret = w->event(w,
-- 
2.17.1