Re: [PATCH 0/7] cxl: Consolidate cxlmd->endpoint accessing

[Li Ming <ming.li@zohomail.com>]

在 2026/3/11 04:33, Dan Williams 写道:
> Li Ming wrote:
>> Currently, CXL subsystem implementation has some functions that may
>> access CXL memdev's endpoint before the endpoint initialization
>> completed or without checking the CXL memdev endpoint validity.
>> This patchset fixes three scenarios as above description.
>>
>> 1. cxl_dpa_to_region() is possible to access an invalid CXL memdev
>>     endpoint.
>>     there are two scenarios that can trigger this issue:
>>     a. memdev poison injection/clearing debugfs interfaces:
>>        devm_cxl_add_endpoint() is used to register CXL memdev endpoint
>>        and update cxlmd->endpoint from -ENXIO to the endpoint structure.
>>        memdev poison injection/clearing debugfs interfaces are registered
>>        before devm_cxl_add_endpoint() is invoked in cxl_mem_probe().
>>        There is a small window where user can use the debugfs interfaces
>>        to access an invalid endpoint.
> This is the justification I wanted to see in the changelog of the
> patches themselves. That is a reasonable theoretical window.
>
>>     b. cxl_event_config() in the end of cxl_pci_probe():
>>        cxl_event_config() invokes cxl_mem_get_event_record() to get
>>        remain event logs from CXL device during cxl_pci_probe(). If CXL
>>        memdev probing failed before that, it is also possible to access
>>        an invalid endpoint.
> Makes sense, please put this in the changelog.
>
>>     To fix these two cases, cxl_dpa_to_region() requires callers holding
>>     CXL memdev lock to access it and check if CXL memdev driver bingding
>>     status. Holding CXL memdev lock ensures that CXL memdev probing has
>>     completed, and if CXL memdev driver is bound, it will mean
>>     cxlmd->endpoint is valid. (PATCH #1-#5)
>>
>> 2. cxl_reset_done() callback in cxl_pci module.
>>     cxl_reset_done() callback also accesses cxlmd->endpoint without any
>>     checking. If CXL memdev probing fails, then cxl_reset_done() is
>>     called by PCI subsystem, it will access an invalid endpoint. The
>>     solution is adding a CXL memdev driver binding status inside
>>     cxl_reset_done(). (PATCH #6)
> Makes sense. I jumped into the patches first since I was familiar with
> the problem space, but happy to see you did this analysis. Just
> cover-letter analysis can typically get lost in teh shuffle.
>
Thanks for review, Will do you mentioned above.


Ming