Messages in this thread | | | Date | Thu, 18 Jun 2015 01:22:50 +0100 | Subject | Re: mm: shmem_zero_setup skip security check and lockdep conflict with XFS | From | Hugh Dickins <> |
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Wed, Jun 17, 2015 at 12:45 PM, Morten Stevens <mstevens@fedoraproject.org> wrote: > 2015-06-15 8:09 GMT+02:00 Daniel Wagner <wagi@monom.org>: >> On 06/14/2015 06:48 PM, Hugh Dickins wrote: >>> It appears that, at some point last year, XFS made directory handling >>> changes which bring it into lockdep conflict with shmem_zero_setup(): >>> it is surprising that mmap() can clone an inode while holding mmap_sem, >>> but that has been so for many years. >>> >>> Since those few lockdep traces that I've seen all implicated selinux, >>> I'm hoping that we can use the __shmem_file_setup(,,,S_PRIVATE) which >>> v3.13's commit c7277090927a ("security: shmem: implement kernel private >>> shmem inodes") introduced to avoid LSM checks on kernel-internal inodes: >>> the mmap("/dev/zero") cloned inode is indeed a kernel-internal detail. >>> >>> This also covers the !CONFIG_SHMEM use of ramfs to support /dev/zero >>> (and MAP_SHARED|MAP_ANONYMOUS). I thought there were also drivers >>> which cloned inode in mmap(), but if so, I cannot locate them now. >>> >>> Reported-and-tested-by: Prarit Bhargava <prarit@redhat.com> >>> Reported-by: Daniel Wagner <wagi@monom.org> >> >> Reported-and-tested-by: Daniel Wagner <wagi@monom.org> >> >> Sorry for the long delay. It took me a while to figure out my original >> setup. I could verify that this patch made the lockdep message go away >> on 4.0-rc6 and also on 4.1-rc8. > > Yes, it's also fixed for me after applying this patch to 4.1-rc8.
Thank you - Hugh
> > Best regards, > > Morten
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