[BUG] usb: dwc3: Kernel NULL pointer dereference in dwc3_remove()

[Alexandru Elisei]

I've been seeing the following panic when shutting down my rockpro64:

[   21.459064] xhci-hcd xhci-hcd.0.auto: USB bus 5 deregistered
[   21.683077] Unable to handle kernel NULL pointer dereference at virtual address
00000000000000a0
[   21.683858] Mem abort info:
[   21.684104]   ESR = 0x96000004
[   21.684375]   EC = 0x25: DABT (current EL), IL = 32 bits
[   21.684841]   SET = 0, FnV = 0
[   21.685111]   EA = 0, S1PTW = 0
[   21.685389] Data abort info:
[   21.685644]   ISV = 0, ISS = 0x00000004
[   21.686024]   CM = 0, WnR = 0
[   21.686288] user pgtable: 4k pages, 48-bit VAs, pgdp=000000000757a000
[   21.686853] [00000000000000a0] pgd=0000000000000000, p4d=0000000000000000
[   21.687452] Internal error: Oops: 96000004EEMPT SMP
[   21.687941] Modules linked in:
[   21.688214] CPU: 4 PID: 1 Comm: shutdown Not tainted
5.12.0-rc7-00262-g568262bf5492 #33
[   21.688915] Hardware name: Pine64 RockPro64 v2.0 (DT)
[   21.689357] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
[   21.689884] pc : down_read_interruptible+0xec/0x200
[   21.690321] lr : simple_recursive_removal+0x48/0x280
[   21.690761] sp : ffff800011f4b940
[   21.691053] x29: ffff800011f4b940 x28: ffff000000809b40
[   21.691522] x27: ffff000000809b98 x26: ffff8000114f5170
[   21.691990] x25: 00000000000000a0 x24: ffff800011e84030
[   21.692459] x23: 0000000000000080 x22: 0000000000000000
[   21.692927] x21: ffff800011ecaa5c x20: ffff800011ecaa60
[   21.693395] x19: ffff000000809b40 x18: ffffffffffffffff
[   21.693863] x17: 0000000000000000 x16: 0000000000000000
[   21.694331] x15: ffff800091f4ba6d x14: 0000000000000004
[   21.694799] x13: 0000000000000000 x12: 0000000000000020
[   21.695267] x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f
[   21.695735] x9 : 6f6c746364716e62 x8 : 7f7f7f7f7f7f7f7f
[   21.696203] x7 : fefefeff6364626d x6 : 0000000000001bd8
[   21.696671] x5 : 0000000000000000 x4 : 0000000000000000
[   21.697138] x3 : 00000000000000a0 x2 : 0000000000000001
[   21.697606] x1 : 0000000000000000 x0 : 00000000000000a0
[   21.698075] Call trace:
[   21.698291]  down_read_interruptible+0xec/0x200
[   21.698690]  debugfs_remove+0x60/0x84
[   21.699016]  dwc3_debugfs_exit+0x1c/0x6c
[   21.699363]  dwc3_remove+0x34/0x1a0
[   21.699672]  platform_remove+0x28/0x60
[   21.700005]  __device_release_driver+0x188/0x230
[   21.700414]  device_release_driver+0x2c/0x44
[   21.700791]  bus_remove_device+0x124/0x130
[   21.701154]  device_del+0x168/0x420
[   21.701462]  platform_device_del.part.0+0x1c/0x90
[   21.701877]  platform_device_unregister+0x28/0x44
[   21.702291]  of_platform_device_destroy+0xe8/0x100
[   21.702716]  device_for_each_child_reverse+0x64/0xb4
[   21.703153]  of_platform_depopulate+0x40/0x84
[   21.703538]  __dwc3_of_simple_teardown+0x20/0xd4
[   21.703945]  dwc3_of_simple_shutdown+0x14/0x20
[   21.704337]  platform_shutdown+0x28/0x40
[   21.704683]  device_shutdown+0x158/0x330
[   21.705029]  kernel_power_off+0x38/0x7c
[   21.705372]  __do_sys_reboot+0x16c/0x2a0
[   21.705719]  __arm64_sys_reboot+0x28/0x34
[   21.706074]  el0_svc_common.constprop.0+0x60/0x120
[   21.706499]  do_el0_svc+0x28/0x94
[   21.706794]  el0_svc+0x2c/0x54
[   21.707067]  el0_sync_handler+0xa4/0x130
[   21.707414]  el0_sync+0x170/0x180
[   21.707711] Code: c8047c62 35ffff84 17fffe5f f9800071 (c85ffc60)
[   21.708250] ---[ end trace 5ae08147542eb468 ]---
[   21.708667] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[   21.709456] Kernel Offset: disabled
[   21.709762] CPU features: 0x00240022,2100600c
[   21.710146] Memory Limit: 2048 MB
[   21.710443] ---[ end Kernel panic - not syncing: Attempted to kill init!
exitcode=0x0000000b ]---

I've been able to bisect the panic and the offending commit is 568262bf5492 ("usb:
dwc3: core: Add shutdown callback for dwc3"). I can provide more diagnostic
information if needed and I can help test the fix.

Thanks,

Alex