On Mon, Jun 15, 2015 at 5:58 AM, Morten Stevens <mstevens@xxxxxxxxxxxxxxxxx> wrote: > Hi Josh, > > Could you please add this patch to the 4.1-rc8 kernel for rawhide? > > https://lkml.org/lkml/2015/6/14/169 Done. I'd been watching that thread as well. As an aside, it is better to send such requests to the Fedora kernel list (CC'd now.) That way everyone sees it and it doesn't get lost in someone's inbox. josh > mm: shmem_zero_setup skip security check and lockdep conflict with XFS > > 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@xxxxxxxxxx> > Reported-by: Daniel Wagner <wagi@xxxxxxxxx> > Reported-by: Morten Stevens <mstevens@xxxxxxxxxxxxxxxxx> > Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> > --- > mm/shmem.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > --- 4.1-rc7/mm/shmem.c 2015-04-26 19:16:31.352191298 -0700 > +++ linux/mm/shmem.c 2015-06-14 09:26:49.461120166 -0700 > @@ -3401,7 +3401,13 @@ int shmem_zero_setup(struct vm_area_stru > struct file *file; > loff_t size = vma->vm_end - vma->vm_start; > > - file = shmem_file_setup("dev/zero", size, vma->vm_flags); > + /* > + * Cloning a new file under mmap_sem leads to a lock ordering > conflict > + * between XFS directory reading and selinux: since this file is > only > + * accessible to the user through its mapping, use S_PRIVATE flag to > + * bypass file security, in the same way as > shmem_kernel_file_setup(). > + */ > + file = __shmem_file_setup("dev/zero", size, vma->vm_flags, > S_PRIVATE); > if (IS_ERR(file)) > return PTR_ERR(file); > > > Thank you, > > Best regards, > > Morten _______________________________________________ kernel mailing list kernel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/kernel
