This is a note to let you know that I've just added the patch titled ALSA: info: Drop WARN_ON() from buffer NULL sanity check to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: alsa-info-drop-warn_on-from-buffer-null-sanity-check.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 60379ba08532eca861e933b389526a4dc89e0c42 Mon Sep 17 00:00:00 2001 From: Takashi Iwai <tiwai@xxxxxxx> Date: Fri, 17 Jul 2020 10:40:23 +0200 Subject: ALSA: info: Drop WARN_ON() from buffer NULL sanity check From: Takashi Iwai <tiwai@xxxxxxx> commit 60379ba08532eca861e933b389526a4dc89e0c42 upstream. snd_info_get_line() has a sanity check of NULL buffer -- both buffer itself being NULL and buffer->buffer being NULL. Basically both checks are valid and necessary, but the problem is that it's with snd_BUG_ON() macro that triggers WARN_ON(). The latter condition (NULL buffer->buffer) can be met arbitrarily by user since the buffer is allocated at the first write, so it means that user can trigger WARN_ON() at will. This patch addresses it by simply moving buffer->buffer NULL check out of snd_BUG_ON() so that spurious WARNING is no longer triggered. Reported-by: syzbot+e42d0746c3c3699b6061@xxxxxxxxxxxxxxxxxxxxxxxxx Cc: <stable@xxxxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20200717084023.5928-1-tiwai@xxxxxxx Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/core/info.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/sound/core/info.c +++ b/sound/core/info.c @@ -634,7 +634,9 @@ int snd_info_get_line(struct snd_info_bu { int c = -1; - if (snd_BUG_ON(!buffer || !buffer->buffer)) + if (snd_BUG_ON(!buffer)) + return 1; + if (!buffer->buffer) return 1; if (len <= 0 || buffer->stop || buffer->error) return 1; Patches currently in stable-queue which might be from tiwai@xxxxxxx are queue-4.14/alsa-info-drop-warn_on-from-buffer-null-sanity-check.patch