Messages in this thread | | | Subject | Re: [PATCH] mm,hwpoison: return -EBUSY when page already poisoned | From | David Hildenbrand <> | Date | Wed, 24 Feb 2021 11:10:23 +0100 |
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On 24.02.21 08:16, Aili Yao wrote: > When the page is already poisoned, another memory_failure() call in the > same page now return 0, meaning OK. For nested memory mce handling, this > behavior may lead real serious problem, Example: > > 1.When LCME is enabled, and there are two processes A && B running on > different core X && Y separately, which will access one same page, then > the page corrupted when process A access it, a MCE will be rasied to > core X and the error process is just underway. > > 2.Then B access the page and trigger another MCE to core Y, it will also > do error process, it will see TestSetPageHWPoison be true, and 0 is > returned. > > 3.The kill_me_maybe will check the return: > > 1244 static void kill_me_maybe(struct callback_head *cb) > 1245 { > > 1254 if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags) && > 1255 !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) { > 1256 set_mce_nospec(p->mce_addr >> PAGE_SHIFT, > p->mce_whole_page); > 1257 sync_core(); > 1258 return; > 1259 } > > 1267 } > > 4. The error process for B will end, and may nothing happened if > kill-early is not set, We may let the wrong data go into effect. > > For other cases which care the return value of memory_failure() should > check why they want to process a memory error which have already been > processed. This behavior seems reasonable. > > In kill_me_maybe, log the fact about the memory may not recovered, and > we will kill the related process. >
Is -EBUSY then the right return value?
I'd expect if it's already poisoned that we would get something like EHWPOISON.
Does this affect existing user space interfaces (especially, via madvise?)?
-- Thanks,
David / dhildenb
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