linux-kernel - [PATCH v2] soc: soc-dapm: fix two incorrect uses of list iterator

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Message-Id: <20220329012134.9375-1-xiam0nd.tong@gmail.com>
Date:   Tue, 29 Mar 2022 09:21:34 +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 v2] 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 continue the outer list_for_each_entry_safe()
loop with the same entry if w->event is NULL, but misunderstanding the
meaning of list_for_each_entry_safe_continue().

So just add a 'continue;' 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>
---

changes since v1:
 - use continue statement instead (Mark Brown)

v1:https://lore.kernel.org/lkml/20220327082138.13696-1-xiam0nd.tong@gmail.com/

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

diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index b06c5682445c..fb43b331a36e 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1687,8 +1687,7 @@ static void dapm_seq_run(struct snd_soc_card *card,
 		switch (w->id) {
 		case snd_soc_dapm_pre:
 			if (!w->event)
-				list_for_each_entry_safe_continue(w, n, list,
-								  power_list);
+				continue;
 
 			if (event == SND_SOC_DAPM_STREAM_START)
 				ret = w->event(w,
@@ -1700,8 +1699,7 @@ static void dapm_seq_run(struct snd_soc_card *card,
 
 		case snd_soc_dapm_post:
 			if (!w->event)
-				list_for_each_entry_safe_continue(w, n, list,
-								  power_list);
+				continue;
 
 			if (event == SND_SOC_DAPM_STREAM_START)
 				ret = w->event(w,
-- 
2.17.1