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@perex.cz>
Link: https://lore.kernel.org/r/20230523075358.9672-18-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/core/seq/seq_memory.c b/sound/core/seq/seq_memory.c
index 47ef6bc..c8d26bc 100644 (file)
--- 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);