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. [1]: https://lore.kernel.org/linux-mm/20201013013416.390574-1-dima@xxxxxxxxxx/ Thanks, Dmitry
