linux-kernel - [PATCH v2 17/37] ALSA: seq: Clear padded bytes at expanding events

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Date:   Tue, 23 May 2023 09:53:38 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     alsa-devel@...a-project.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH v2 17/37] ALSA: seq: Clear padded bytes at expanding events

There can be a small memory hole that may not be cleared at expanding
an event with the variable length type.  Make sure to clear it.

Reviewed-by: Jaroslav Kysela <perex@...ex.cz>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 sound/core/seq/seq_memory.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
index 47ef6bc30c0e..c8d26bce69ff 100644
--- a/sound/core/seq/seq_memory.c
+++ b/sound/core/seq/seq_memory.c
@@ -152,12 +152,16 @@ int snd_seq_expand_var_event(const struct snd_seq_event *event, int count, char
 			return -EINVAL;
 		if (copy_from_user(buf, (void __force __user *)event->data.ext.ptr, len))
 			return -EFAULT;
-		return newlen;
+	} else {
+		err = snd_seq_dump_var_event(event,
+					     in_kernel ? seq_copy_in_kernel : seq_copy_in_user,
+					     &buf);
+		if (err < 0)
+			return err;
 	}
-	err = snd_seq_dump_var_event(event,
-				     in_kernel ? seq_copy_in_kernel : seq_copy_in_user,
-				     &buf);
-	return err < 0 ? err : newlen;
+	if (len != newlen)
+		memset(buf + len, 0, newlen - len);
+	return newlen;
 }
 EXPORT_SYMBOL(snd_seq_expand_var_event);
 
-- 
2.35.3