diff options
| author | David Herrmann <dh.herrmann@gmail.com> | 2014-08-08 14:25:25 -0700 |
|---|---|---|
| committer | Maciej Wereski <m.wereski@partner.samsung.com> | 2014-12-29 09:31:35 +0100 |
| commit | f5eb589a8cff825e57d6cb42d84c9ae61f2e1baf (patch) | |
| tree | bbf7ed91762f0dcfabe0e278901d4270f6d93367 /kernel | |
| parent | 5988dd09c4983bed7c2671446de5715a63036bb3 (diff) | |
| download | linux-3.10-f5eb589a8cff825e57d6cb42d84c9ae61f2e1baf.tar.gz linux-3.10-f5eb589a8cff825e57d6cb42d84c9ae61f2e1baf.tar.bz2 linux-3.10-f5eb589a8cff825e57d6cb42d84c9ae61f2e1baf.zip | |
mm: allow drivers to prevent new writable mappings
This patch (of 6):
The i_mmap_writable field counts existing writable mappings of an
address_space. To allow drivers to prevent new writable mappings, make
this counter signed and prevent new writable mappings if it is negative.
This is modelled after i_writecount and DENYWRITE.
This will be required by the shmem-sealing infrastructure to prevent any
new writable mappings after the WRITE seal has been set. In case there
exists a writable mapping, this operation will fail with EBUSY.
Note that we rely on the fact that iff you already own a writable mapping,
you can increase the counter without using the helpers. This is the same
that we do for i_writecount.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Ryan Lortie <desrt@desrt.ca>
Cc: Lennart Poettering <lennart@poettering.net>
Cc: Daniel Mack <zonque@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: If33fdcedbcf202ab177c4e21afc7eec261088a8b
Origin: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=4bb5f5d9395bc112d93a134d8f5b05611eddc9c0
Backported-by: Maciej Wereski <m.wereski@partner.samsung.com>
Signed-off-by: Maciej Wereski <m.wereski@partner.samsung.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/fork.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 514dbc40f98..219a0fc2f7f 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -422,7 +422,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) atomic_dec(&inode->i_writecount); mutex_lock(&mapping->i_mmap_mutex); if (tmp->vm_flags & VM_SHARED) - mapping->i_mmap_writable++; + atomic_inc(&mapping->i_mmap_writable); flush_dcache_mmap_lock(mapping); /* insert tmp into the share list, just after mpnt */ if (unlikely(tmp->vm_flags & VM_NONLINEAR)) |