On Mon, Mar 11, 2019 at 06:41:03PM +0200, Andy Shevchenko wrote:
> If SSDT overlay is loaded via ConfigFS and then unloaded the device,
> we would like to have OF modalias for, already gone. Thus, acpi_get_name()
> returns no allocated buffer for such case and kernel crashes afterwards:
>
> ACPI: Host-directed Dynamic ACPI Table Unload
> ads7950 spi-PRP0001:00: Dropping the link to regulator.0
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
> #PF error: [normal kernel read fault]
> PGD 80000000070d6067 P4D 80000000070d6067 PUD 70d0067 PMD 0
> Oops: 0000 [#1] SMP PTI
> CPU: 0 PID: 40 Comm: kworker/u4:2 Not tainted 5.0.0+ #96
> Hardware name: Intel Corporation Merrifield/BODEGA BAY, BIOS 542 2015.01.21:18.19.48
> Workqueue: kacpi_hotplug acpi_device_del_work_fn
> RIP: 0010:create_of_modalias.isra.1+0x4c/0x150
> Code: 00 00 48 89 44 24 18 31 c0 48 8d 54 24 08 48 c7 44 24 10 00 00 00 00 48 c7 44 24 08 ff ff ff ff e8 7a b0 03 00 48 8b 4c 24 10 <0f> b6 01 84 c0 74 27 48 c7 c7 00 09 f4 a5 0f b6 f0 8d 50 20 f6 04
> RSP: 0000:ffffa51040297c10 EFLAGS: 00010246
> RAX: 0000000000001001 RBX: 0000000000000785 RCX: 0000000000000000
> RDX: 0000000000001001 RSI: 0000000000000286 RDI: ffffa2163dc042e0
> RBP: ffffa216062b1196 R08: 0000000000001001 R09: ffffa21639873000
> R10: ffffffffa606761d R11: 0000000000000001 R12: ffffa21639873218
> R13: ffffa2163deb5060 R14: ffffa216063d1010 R15: 0000000000000000
> FS: 0000000000000000(0000) GS:ffffa2163e000000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000000000000 CR3: 0000000007114000 CR4: 00000000001006f0
> Call Trace:
> __acpi_device_uevent_modalias+0xb0/0x100
> spi_uevent+0xd/0x40
>
> ...
>
> In order to fix above let create_of_modalias() check the status returned
> by acpi_get_name() and bail out in case of failure.
>
> Fixes: 8765c5ba1949 ("ACPI / scan: Rework modalias creation when "compatible" is present")
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=201381
> Reported-by: Ferry Toth <fntoth@xxxxxxxxx>
> Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
