syzbot reported null pointer dereference in usb_audio_probe. The problem was in case, when quirk == NULL. It's not an error condition, so quirk must be checked before dereferencing.

Call Trace: usb_probe_interface+0x315/0x7f0 drivers/usb/core/driver.c:396 really_probe+0x291/0xe60 drivers/base/dd.c:554 driver_probe_device+0x26b/0x3d0 drivers/base/dd.c:740 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:846 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 __device_attach+0x228/0x4a0 drivers/base/dd.c:914 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0xbdb/0x1db0 drivers/base/core.c:3242 usb_set_configuration+0x113f/0x1910 drivers/usb/core/message.c:2164 usb_generic_driver_probe+0xba/0x100 drivers/usb/core/generic.c:238 usb_probe_device+0xd9/0x2c0 drivers/usb/core/driver.c:293 really_probe+0x291/0xe60 drivers/base/dd.c:554 driver_probe_device+0x26b/0x3d0 drivers/base/dd.c:740 __device_attach_driver+0x1d1/0x290 drivers/base/dd.c:846 bus_for_each_drv+0x15f/0x1e0 drivers/base/bus.c:431 __device_attach+0x228/0x4a0 drivers/base/dd.c:914 bus_probe_device+0x1e4/0x290 drivers/base/bus.c:491 device_add+0xbdb/0x1db0 drivers/base/core.c:3242 usb_new_device.cold+0x721/0x1058 drivers/usb/core/hub.c:2555 hub_port_connect drivers/usb/core/hub.c:5223 [inline] hub_port_connect_change drivers/usb/core/hub.c:5363 [inline] port_event drivers/usb/core/hub.c:5509 [inline] hub_event+0x2357/0x4320 drivers/usb/core/hub.c:5591 process_one_work+0x98d/0x1600 kernel/workqueue.c:2275 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421 kthread+0x3b1/0x4a0 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Reported-by: syzbot+719da9b149a931f5143f@syzkaller.appspotmail.com Fixes: 9799110825db ("ALSA: usb-audio: Disable USB autosuspend properly in setup_disable_autosuspend()") Signed-off-by: Pavel Skripkin paskripkin@gmail.com --- sound/usb/card.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c index 08c794883299..3fd1743513b5 100644 --- a/sound/usb/card.c +++ b/sound/usb/card.c @@ -830,7 +830,8 @@ static int usb_audio_probe(struct usb_interface *intf, snd_media_device_create(chip, intf); }

- chip->quirk_type = quirk->type; + if (quirk) + chip->quirk_type = quirk->type;

usb_chip[chip->index] = chip; chip->intf[chip->num_interfaces] = intf;

The problem was in wrong "if" placement. chip->quirk_type is freed in snd_card_free_when_closed(), but inside if statement it's accesed.

Fixes: 9799110825db ("ALSA: usb-audio: Disable USB autosuspend properly in setup_disable_autosuspend()" Signed-off-by: Pavel Skripkin paskripkin@gmail.com --- sound/usb/card.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c index 3fd1743513b5..b6f4c0848e66 100644 --- a/sound/usb/card.c +++ b/sound/usb/card.c @@ -907,6 +907,9 @@ static void usb_audio_disconnect(struct usb_interface *intf) } }

+ if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND) + usb_enable_autosuspend(interface_to_usbdev(intf)); + chip->num_interfaces--; if (chip->num_interfaces <= 0) { usb_chip[chip->index] = NULL; @@ -915,9 +918,6 @@ static void usb_audio_disconnect(struct usb_interface *intf) } else { mutex_unlock(&register_mutex); } - - if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND) - usb_enable_autosuspend(interface_to_usbdev(intf)); }

/* lock the shutdown (disconnect) task and autoresume */