From: Takashi Iwai <tiwai@suse.de> stable inclusion from stable-5.10.75 commit 7680631ac7ab14b5061b475605f469d87952e1b1 bugzilla: 182987 https://gitee.com/openeuler/kernel/issues/I4I3MP Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 1f8763c59c4ec6254d629fe77c0a52220bd907aa upstream. John Keeping reported and posted a patch for a potential UAF in rawmidi sequencer destruction: the snd_rawmidi_dev_seq_free() may be called after the associated rawmidi object got already freed. After a deeper look, it turned out that the bug is rather the incorrect private_free call order for a snd_seq_device. The snd_seq_device private_free gets called at the release callback of the sequencer device object, while this was rather expected to be executed at the snd_device call chains that runs at the beginning of the whole card-free procedure. It's been broken since the rewrite of sequencer-device binding (although it hasn't surfaced because the sequencer device release happens usually right along with the card device release). This patch corrects the private_free call to be done in the right place, at snd_seq_device_dev_free(). Fixes: 7c37ae5c625a ("ALSA: seq: Rewrite sequencer device binding with standard bus") Reported-and-tested-by: John Keeping <john@metanate.com> Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20210930114114.8645-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Chen Jun <chenjun102@huawei.com> Acked-by: Weilong Chen <chenweilong@huawei.com> Signed-off-by: Chen Jun <chenjun102@huawei.com> --- sound/core/seq_device.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/sound/core/seq_device.c b/sound/core/seq_device.c index 7ed13cb32ef8..f22d3bbfcaa5 100644 --- a/sound/core/seq_device.c +++ b/sound/core/seq_device.c @@ -147,6 +147,8 @@ static int snd_seq_device_dev_free(struct snd_device *device) struct snd_seq_device *dev = device->device_data; cancel_autoload_drivers(); + if (dev->private_free) + dev->private_free(dev); put_device(&dev->dev); return 0; } @@ -174,11 +176,7 @@ static int snd_seq_device_dev_disconnect(struct snd_device *device) static void snd_seq_dev_release(struct device *dev) { - struct snd_seq_device *sdev = to_seq_dev(dev); - - if (sdev->private_free) - sdev->private_free(sdev); - kfree(sdev); + kfree(to_seq_dev(dev)); } /* -- 2.20.1