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    Subject[PATCH 4.4 15/28] ALSA: usb-audio: Kill stray URB at exiting
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Takashi Iwai <tiwai@suse.de>

    commit 124751d5e63c823092060074bd0abaae61aaa9c4 upstream.

    USB-audio driver may leave a stray URB for the mixer interrupt when it
    exits by some error during probe. This leads to a use-after-free
    error as spotted by syzkaller like:
    ==================================================================
    BUG: KASAN: use-after-free in snd_usb_mixer_interrupt+0x604/0x6f0
    Call Trace:
    <IRQ>
    __dump_stack lib/dump_stack.c:16
    dump_stack+0x292/0x395 lib/dump_stack.c:52
    print_address_description+0x78/0x280 mm/kasan/report.c:252
    kasan_report_error mm/kasan/report.c:351
    kasan_report+0x23d/0x350 mm/kasan/report.c:409
    __asan_report_load8_noabort+0x19/0x20 mm/kasan/report.c:430
    snd_usb_mixer_interrupt+0x604/0x6f0 sound/usb/mixer.c:2490
    __usb_hcd_giveback_urb+0x2e0/0x650 drivers/usb/core/hcd.c:1779
    ....

    Allocated by task 1484:
    save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
    save_stack+0x43/0xd0 mm/kasan/kasan.c:447
    set_track mm/kasan/kasan.c:459
    kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
    kmem_cache_alloc_trace+0x11e/0x2d0 mm/slub.c:2772
    kmalloc ./include/linux/slab.h:493
    kzalloc ./include/linux/slab.h:666
    snd_usb_create_mixer+0x145/0x1010 sound/usb/mixer.c:2540
    create_standard_mixer_quirk+0x58/0x80 sound/usb/quirks.c:516
    snd_usb_create_quirk+0x92/0x100 sound/usb/quirks.c:560
    create_composite_quirk+0x1c4/0x3e0 sound/usb/quirks.c:59
    snd_usb_create_quirk+0x92/0x100 sound/usb/quirks.c:560
    usb_audio_probe+0x1040/0x2c10 sound/usb/card.c:618
    ....

    Freed by task 1484:
    save_stack_trace+0x1b/0x20 arch/x86/kernel/stacktrace.c:59
    save_stack+0x43/0xd0 mm/kasan/kasan.c:447
    set_track mm/kasan/kasan.c:459
    kasan_slab_free+0x72/0xc0 mm/kasan/kasan.c:524
    slab_free_hook mm/slub.c:1390
    slab_free_freelist_hook mm/slub.c:1412
    slab_free mm/slub.c:2988
    kfree+0xf6/0x2f0 mm/slub.c:3919
    snd_usb_mixer_free+0x11a/0x160 sound/usb/mixer.c:2244
    snd_usb_mixer_dev_free+0x36/0x50 sound/usb/mixer.c:2250
    __snd_device_free+0x1ff/0x380 sound/core/device.c:91
    snd_device_free_all+0x8f/0xe0 sound/core/device.c:244
    snd_card_do_free sound/core/init.c:461
    release_card_device+0x47/0x170 sound/core/init.c:181
    device_release+0x13f/0x210 drivers/base/core.c:814
    ....

    Actually such a URB is killed properly at disconnection when the
    device gets probed successfully, and what we need is to apply it for
    the error-path, too.

    In this patch, we apply snd_usb_mixer_disconnect() at releasing.
    Also introduce a new flag, disconnected, to struct usb_mixer_interface
    for not performing the disconnection procedure twice.

    Reported-by: Andrey Konovalov <andreyknvl@google.com>
    Tested-by: Andrey Konovalov <andreyknvl@google.com>
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    sound/usb/mixer.c | 12 ++++++++++--
    sound/usb/mixer.h | 2 ++
    2 files changed, 12 insertions(+), 2 deletions(-)

    --- a/sound/usb/mixer.c
    +++ b/sound/usb/mixer.c
    @@ -2161,6 +2161,9 @@ static int parse_audio_unit(struct mixer

    static void snd_usb_mixer_free(struct usb_mixer_interface *mixer)
    {
    + /* kill pending URBs */
    + snd_usb_mixer_disconnect(mixer);
    +
    kfree(mixer->id_elems);
    if (mixer->urb) {
    kfree(mixer->urb->transfer_buffer);
    @@ -2504,8 +2507,13 @@ _error:

    void snd_usb_mixer_disconnect(struct usb_mixer_interface *mixer)
    {
    - usb_kill_urb(mixer->urb);
    - usb_kill_urb(mixer->rc_urb);
    + if (mixer->disconnected)
    + return;
    + if (mixer->urb)
    + usb_kill_urb(mixer->urb);
    + if (mixer->rc_urb)
    + usb_kill_urb(mixer->rc_urb);
    + mixer->disconnected = true;
    }

    #ifdef CONFIG_PM
    --- a/sound/usb/mixer.h
    +++ b/sound/usb/mixer.h
    @@ -22,6 +22,8 @@ struct usb_mixer_interface {
    struct urb *rc_urb;
    struct usb_ctrlrequest *rc_setup_packet;
    u8 rc_buffer[6];
    +
    + bool disconnected;
    };

    #define MAX_CHANNELS 16 /* max logical channels */

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