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05 April 2024, 19:05:47 UTC
Revision 66fc13039422ba7df2d01a8ee0873e4ef965b50b authored by Hugh Dickins on 14 June 2015, 16:48:09 UTC, committed by Linus Torvalds on 18 June 2015, 06:40:19 UTC 
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@redhat.com>
Reported-and-tested-by: Daniel Wagner <wagi@monom.org>
Reported-and-tested-by: Morten Stevens <mstevens@fedoraproject.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent 0f57d86
History
Tip revision: 66fc13039422ba7df2d01a8ee0873e4ef965b50b authored by Hugh Dickins on 14 June 2015, 16:48:09 UTC
mm: shmem_zero_setup skip security check and lockdep conflict with XFS
Tip revision: 66fc130
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