Re: [PATCH] powerpc/iommu: Fix the missing iommu_group_put() during platform domain attach

[Michael Ellerman]

Venkat Rao Bagalkote <venkat88@xxxxxxxxxxxxxxxxxx> writes:
> Thanks for the patch. Applied this patch and verified and issue is fixed.
>
> This issue way originally reported in the below mail.
>
> https://marc.info/?l=linux-kernel&m=170737160630106&w=2

Please use lore for links, in this case:

https://lore.kernel.org/all/274e0d2b-b5cc-475e-94e6-8427e88e271d@xxxxxxxxxxxxxxxxxx/

cheers

> On 13/02/24 10:51 pm, Jason Gunthorpe wrote:
>> On Tue, Feb 13, 2024 at 10:05:22AM -0600, Shivaprasad G Bhat wrote:
>>> The function spapr_tce_platform_iommu_attach_dev() is missing to call
>>> iommu_group_put() when the domain is already set. This refcount leak
>>> shows up with BUG_ON() during DLPAR remove operation as,
>>>
>>>    KernelBug: Kernel bug in state 'None': kernel BUG at arch/powerpc/platforms/pseries/iommu.c:100!
>>>    Oops: Exception in kernel mode, sig: 5 [#1]
>>>    LE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=8192 NUMA pSeries
>>>    <snip>
>>>    Hardware name: IBM,9080-HEX POWER10 (raw) 0x800200 0xf000006 of:IBM,FW1060.00 (NH1060_016) hv:phyp pSeries
>>>    NIP:  c0000000000ff4d4 LR: c0000000000ff4cc CTR: 0000000000000000
>>>    REGS: c0000013aed5f840 TRAP: 0700   Tainted: G          I         (6.8.0-rc3-autotest-g99bd3cb0d12e)
>>>    MSR:  8000000000029033 <SF,EE,ME,IR,DR,RI,LE>  CR: 44002402  XER: 20040000
>>>    CFAR: c000000000a0d170 IRQMASK: 0
>>>    GPR00: c0000000000ff4cc c0000013aed5fae0 c000000001512700 c0000013aa362138
>>>    GPR04: 0000000000000000 0000000000000000 0000000000000000 0000000119c8afd0
>>>    GPR08: 0000000000000000 c000001284442b00 0000000000000001 0000000000001003
>>>    GPR12: 0000000300000000 c0000018ffff2f00 0000000000000000 0000000000000000
>>>    GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>>>    GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
>>>    GPR24: c0000013aed5fc40 0000000000000002 0000000000000000 c000000002757d90
>>>    GPR28: c0000000000ff440 c000000002757cb8 c00000183799c1a0 c0000013aa362b00
>>>    NIP [c0000000000ff4d4] iommu_reconfig_notifier+0x94/0x200
>>>    LR [c0000000000ff4cc] iommu_reconfig_notifier+0x8c/0x200
>>>    Call Trace:
>>>    [c0000013aed5fae0] [c0000000000ff4cc] iommu_reconfig_notifier+0x8c/0x200 (unreliable)
>>>    [c0000013aed5fb10] [c0000000001a27b0] notifier_call_chain+0xb8/0x19c
>>>    [c0000013aed5fb70] [c0000000001a2a78] blocking_notifier_call_chain+0x64/0x98
>>>    [c0000013aed5fbb0] [c000000000c4a898] of_reconfig_notify+0x44/0xdc
>>>    [c0000013aed5fc20] [c000000000c4add4] of_detach_node+0x78/0xb0
>>>    [c0000013aed5fc70] [c0000000000f96a8] ofdt_write.part.0+0x86c/0xbb8
>>>    [c0000013aed5fce0] [c00000000069b4bc] proc_reg_write+0xf4/0x150
>>>    [c0000013aed5fd10] [c0000000005bfeb4] vfs_write+0xf8/0x488
>>>    [c0000013aed5fdc0] [c0000000005c0570] ksys_write+0x84/0x140
>>>    [c0000013aed5fe10] [c000000000033358] system_call_exception+0x138/0x330
>>>    [c0000013aed5fe50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec
>>>    --- interrupt: 3000 at 0x20000433acb4
>>>    <snip>
>>>    ---[ end trace 0000000000000000 ]---
>>>
>>> The patch adds the missing iommu_group_put() call.
>>>
>>> Fixes: a8ca9fc9134c ("powerpc/iommu: Do not do platform domain attach atctions after probe")
>>> Signed-off-by: Shivaprasad G Bhat <sbhat@xxxxxxxxxxxxx>
>>> ---
>>>   arch/powerpc/kernel/iommu.c |    4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>> Doh, that is a weird splat for this but thanks for finding it
>>
>> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
>>
>> Jason
>>