Re: memory leak in u_audio_start_playback

[Greg KH]

On Tue, Oct 27, 2020 at 11:50:25AM -0400, Kyungtae Kim wrote:
> On Sun, Oct 25, 2020 at 3:32 PM Kyungtae Kim <kt0755@xxxxxxxxx> wrote:
> >
> > We report a bug (in linux-5.8.13) found by FuzzUSB (a modified version
> > of syzkaller).
> >
> > An instance of struct usb_request allocated in f_audio_set_alt() leaked.
> >
> > ==================================================================
> > BUG: memory leak
> > unreferenced object 0xffff888053df0e00 (size 128):
> >   comm "softirq", pid 0, jiffies 4294940573 (age 17.540s)
> >   hex dump (first 32 bytes):
> >     00 0e df 53 80 88 ff ff 00 0e df 53 80 88 ff ff  ...S.......S....
> >     00 82 df 53 80 88 ff ff c0 00 00 00 00 00 00 00  ...S............
> >   backtrace:
> >     [<000000000694647e>] kmemleak_alloc_recursive include/linux/kmemleak.h:43 [inline]
> >     [<000000000694647e>] slab_post_alloc_hook mm/slab.h:588 [inline]
> >     [<000000000694647e>] slab_alloc_node mm/slub.c:2824 [inline]
> >     [<000000000694647e>] slab_alloc mm/slub.c:2832 [inline]
> >     [<000000000694647e>] kmem_cache_alloc_trace+0x15c/0x310 mm/slub.c:2849
> >     [<00000000d7d91433>] kmalloc include/linux/slab.h:555 [inline]
> >     [<00000000d7d91433>] kzalloc include/linux/slab.h:669 [inline]
> >     [<00000000d7d91433>] dummy_alloc_request+0x83/0x120 drivers/usb/gadget/udc/dummy_hcd.c:663
> >     [<000000006e043557>] usb_ep_alloc_request+0x23/0x170 drivers/usb/gadget/udc/core.c:178
> >     [<00000000fb13871b>] u_audio_start_playback+0x224/0x3c0 drivers/usb/gadget/function/u_audio.c:449
> >     [<0000000017cb1f54>] f_audio_set_alt+0x8e/0x170 drivers/usb/gadget/function/f_uac1.c:463
> >     [<0000000063ba610c>] composite_setup+0x62e/0x2690 drivers/usb/gadget/composite.c:1793
> >     [<00000000e86333ed>] configfs_composite_setup+0xa5/0xd0 drivers/usb/gadget/configfs.c:1457
> >     [<00000000f9a524ea>] dummy_timer+0x5a7/0x1460 drivers/usb/gadget/udc/dummy_hcd.c:1899
> >     [<00000000182f2904>] call_timer_fn+0xdd/0x3a0 kernel/time/timer.c:1416
> >     [<000000000d926b91>] expire_timers kernel/time/timer.c:1461 [inline]
> >     [<000000000d926b91>] __run_timers kernel/time/timer.c:1792 [inline]
> >     [<000000000d926b91>] run_timer_softirq+0x286/0x670 kernel/time/timer.c:1805
> >     [<000000008902fa26>] __do_softirq+0xfa/0x684 kernel/softirq.c:292
> >     [<000000003597f960>] asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
> >     [<000000005c5a9a83>] __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
> >     [<000000005c5a9a83>] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
> >     [<000000005c5a9a83>] do_softirq_own_stack+0x8b/0xb0 arch/x86/kernel/irq_64.c:77
> >     [<00000000590d59e5>] invoke_softirq kernel/softirq.c:387 [inline]
> >     [<00000000590d59e5>] __irq_exit_rcu kernel/softirq.c:417 [inline]
> >     [<00000000590d59e5>] irq_exit_rcu+0xb5/0xf0 kernel/softirq.c:429
> >     [<00000000689d4053>] sysvec_apic_timer_interrupt+0x83/0xf0 arch/x86/kernel/apic/apic.c:1091
> >     [<00000000f2e90960>] asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
> > ==================================================================
> >
> > Regards,
> > Kyungtae Kim

Nice, care to submit a patch to fix this?

We are drowning in syzbot-found issues, almost none will get resolved
unless people start providing resources to fix them.  I would strongly
recommend the people that find them also send a fix at the same time
where ever possible.

thanks,

greg k-h