Messages in this thread | | | Subject | Re: [lkp-robot] [x86/cpu_entry_area] 10043e02db: kernel_BUG_at_arch/x86/mm/physaddr.c | From | Andrey Ryabinin <> | Date | Thu, 28 Dec 2017 19:18:33 +0300 |
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On 12/28/2017 02:54 PM, Dmitry Vyukov wrote: > On Thu, Dec 28, 2017 at 12:51 PM, Thomas Gleixner <tglx@linutronix.de> wrote: >> On Wed, 27 Dec 2017, Dmitry Vyukov wrote: >>> On Wed, Dec 27, 2017 at 7:05 PM, Thomas Gleixner <tglx@linutronix.de> wrote: >>>> So this dies simply because kasan_populate_shadow() runs out of memory and >>>> has no sanity check whatsoever. >>>> >>>> static __init void *early_alloc(size_t size, int nid) >>>> { >>>> return memblock_virt_alloc_try_nid_nopanic(size, size, >>>> __pa(MAX_DMA_ADDRESS), BOOTMEM_ALLOC_ACCESSIBLE, nid); >>>> } >>>> >>>> kasan_populate_pmd() >>>> { >>>> ..... >>>> >>>> p = early_alloc(PAGE_SIZE, nid); >>>> entry = pfn_pte(PFN_DOWN(__pa(p)), PAGE_KERNEL); >>>> >>>> I've instrumented the whole thing and early_alloc() returns NULL at some >>>> point and then __pa(NULL) dies in the VIRTUAL_DEBUG code. Well, it would >>>> die with VIRTUAL_DEBUG=n as well at some other place. >>>> >>>> Not really a problem caused by the patch above, it's merily exposing a code >>>> path which relies blindly on "enough memory available" assumptions. >>>> >>>> Throwing more memory at the VM makes the problem go away... >>> >>> Hi Thomas, >>> >>> We just need a check inside of early_alloc() to properly diagnose such >>> situation, right? >> >> At least you want to panic with a proper out of memory message. But letting >> the thing die at a random place is a bad idea. > > Thanks. I will cook a patch (if Andrey won't beat me to it). >
We probably should panic only if PAGE_SIZE allocation failed. PUD_SIZE,PMD_SIZE allocations have failure fallback. I would suggest add 'bool panic' param to early_alloc() and call memblock_virt_alloc_try_nid() if it's true.
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