Messages in this thread | | | Date | Fri, 28 Jul 2023 16:58:39 -0700 | From | Dan Williams <> | Subject | RE: [PATCH] cxl/memdev: Avoid mailbox functionality on device memory CXL devices |
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Ira Weiny wrote: > Using the proposed type-2 cxl-test device[1] the following > splat was observed: > > BUG: kernel NULL pointer dereference, address: 0000000000000278 > [...] > RIP: 0010:devm_cxl_add_memdev+0x1de/0x2c0 [cxl_core]
It would be useful to decode this to a line number, the rest of this call trace is not adding much.
> [...] > Call Trace: > <TASK> > ? __die+0x1f/0x70 > ? page_fault_oops+0x149/0x420 > ? fixup_exception+0x22/0x310 > ? kernelmode_fixup_or_oops+0x84/0x110 > ? exc_page_fault+0x6d/0x150 > ? asm_exc_page_fault+0x22/0x30 > ? devm_cxl_add_memdev+0x1de/0x2c0 [cxl_core] > cxl_mock_mem_probe+0x632/0x870 [cxl_mock_mem] > platform_probe+0x40/0x90 > really_probe+0x19e/0x3e0 > ? __pfx___driver_attach+0x10/0x10 > __driver_probe_device+0x78/0x160 > driver_probe_device+0x1f/0x90 > __driver_attach+0xce/0x1c0 > bus_for_each_dev+0x63/0xa0 > bus_add_driver+0x112/0x210 > driver_register+0x55/0x100 > ? __pfx_cxl_mock_mem_driver_init+0x10/0x10 [cxl_mock_mem] > [...] > > Commit f6b8ab32e3ec made the mailbox functionality optional. However, > some mailbox functionality was merged after that patch. Therefore some > mailbox functionality can be accessed on a device which did not set up > the mailbox.
cxl_memdev_security_init() definitely needs to move out of devm_cxl_add_memdev() and after that I do not think @mds NULL checks need to be sprinkled everywhere. In other words something is wrong at a higher level if we get into some of these helper functions without the memory device state.
So definitely this uncovered a problem where cxl_memdev_security_init() needs to move, but the rest of the mds NULL checks need clear reproduction scenarios and expect most of them are precluded higher in the call stack.
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