Messages in this thread | | | Subject | Re: [PATCH] x86/mpx: fix recursive munmap() corruption | From | Laurent Dufour <> | Date | Wed, 4 Nov 2020 10:41:32 +0100 |
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Le 03/11/2020 à 22:08, Dmitry Safonov a écrit : > Hi Laurent, Christophe, Michael, all, > > On 11/3/20 5:11 PM, Laurent Dufour wrote: >> Le 23/10/2020 à 14:28, Christophe Leroy a écrit : > [..] >>>>> That seems like it would work for CRIU and make sense in general? >>>> >>>> Sorry for the late answer, yes this would make more sense. >>>> >>>> Here is a patch doing that. >>>> >>> >>> In your patch, the test seems overkill: >>> >>> + if ((start <= vdso_base && vdso_end <= end) || /* 1 */ >>> + (vdso_base <= start && start < vdso_end) || /* 3,4 */ >>> + (vdso_base < end && end <= vdso_end)) /* 2,3 */ >>> + mm->context.vdso_base = mm->context.vdso_end = 0; >>> >>> What about >>> >>> if (start < vdso_end && vdso_start < end) >>> mm->context.vdso_base = mm->context.vdso_end = 0; >>> >>> This should cover all cases, or am I missing something ? >>> >>> >>> And do we really need to store vdso_end in the context ? >>> I think it should be possible to re-calculate it: the size of the VDSO >>> should be (&vdso32_end - &vdso32_start) + PAGE_SIZE for 32 bits VDSO, >>> and (&vdso64_end - &vdso64_start) + PAGE_SIZE for the 64 bits VDSO. >> >> Thanks Christophe for the advise. >> >> That is covering all the cases, and indeed is similar to the Michael's >> proposal I missed last year. >> >> I'll send a patch fixing this issue following your proposal. > > It's probably not necessary anymore. I've sent patches [1], currently in > akpm, the last one forbids splitting of vm_special_mapping. > So, a user is able munmap() or mremap() vdso as a whole, but not partly.
Hi Dmitry,
That's a good thing too, but I think my patch is still valid in the PowerPC code, fixing a bad check, even if some corner cases are handled earlier in the code.
> [1]: > https://lore.kernel.org/linux-mm/20201013013416.390574-1-dima@arista.com/ > > Thanks, > Dmitry >
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