From: Clement Lecigne Date: Fri, 13 Jan 2023 12:07:45 +0000 (+0100) Subject: ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF X-Git-Tag: archive/raspbian/5.10.162-1+rpi1^2~18 X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks:///%22http:/www.example.com/cgi/%22https:/%22bookmarks:/?a=commitdiff_plain;h=cd47767ced9dbb1da188e937538cbcc53de55662;p=linux.git ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=df02234e6b87d2a9a82acd3198e44bdeff8488c6 Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2023-0266 [ Note: this is a fix that works around the bug equivalently as the two upstream commits: 1fa4445f9adf ("ALSA: control - introduce snd_ctl_notify_one() helper") 56b88b50565c ("ALSA: pcm: Move rwsem lock inside snd_ctl_elem_read to prevent UAF") but in a simpler way to fit with older stable trees -- tiwai ] Add missing locking in ctl_elem_read_user/ctl_elem_write_user which can be easily triggered and turned into an use-after-free. Example code paths with SNDRV_CTL_IOCTL_ELEM_READ: 64-bits: snd_ctl_ioctl snd_ctl_elem_read_user [takes controls_rwsem] snd_ctl_elem_read [lock properly held, all good] [drops controls_rwsem] 32-bits (compat): snd_ctl_ioctl_compat snd_ctl_elem_write_read_compat ctl_elem_write_read snd_ctl_elem_read [missing lock, not good] CVE-2023-0266 was assigned for this issue. Signed-off-by: Clement Lecigne Cc: stable@kernel.org # 5.12 and older Signed-off-by: Takashi Iwai Reviewed-by: Jaroslav Kysela Signed-off-by: Greg Kroah-Hartman Gbp-Pq: Topic bugfix/all Gbp-Pq: Name ALSA-pcm-Move-rwsem-lock-inside-snd_ctl_elem_read-to.patch --- diff --git a/sound/core/control_compat.c b/sound/core/control_compat.c index 97467f6a32a..980ab3580f1 100644 --- a/sound/core/control_compat.c +++ b/sound/core/control_compat.c @@ -304,7 +304,9 @@ static int ctl_elem_read_user(struct snd_card *card, err = snd_power_wait(card, SNDRV_CTL_POWER_D0); if (err < 0) goto error; + down_read(&card->controls_rwsem); err = snd_ctl_elem_read(card, data); + up_read(&card->controls_rwsem); if (err < 0) goto error; err = copy_ctl_value_to_user(userdata, valuep, data, type, count); @@ -332,7 +334,9 @@ static int ctl_elem_write_user(struct snd_ctl_file *file, err = snd_power_wait(card, SNDRV_CTL_POWER_D0); if (err < 0) goto error; + down_write(&card->controls_rwsem); err = snd_ctl_elem_write(card, file, data); + up_write(&card->controls_rwsem); if (err < 0) goto error; err = copy_ctl_value_to_user(userdata, valuep, data, type, count);