diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2016-05-20 16:58:36 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-20 17:58:30 -0700 |
| commit | d2005e3f41d4f9299e2df6a967c8beb5086967a9 (patch) | |
| tree | 075dc5ba6de68cfe96acdb91478595e7d3366f2e /include | |
| parent | cd33a76b0f2805fb0d6a05a2d53933f3817ccc9b (diff) | |
userfaultfd: don't pin the user memory in userfaultfd_file_create()
userfaultfd_file_create() increments mm->mm_users; this means that the
memory won't be unmapped/freed if mm owner exits/execs, and UFFDIO_COPY
after that can populate the orphaned mm more.
Change userfaultfd_file_create() and userfaultfd_ctx_put() to use
mm->mm_count to pin mm_struct. This means that
atomic_inc_not_zero(mm->mm_users) is needed when we are going to
actually play with this memory. Except handle_userfault() path doesn't
need this, the caller must already have a reference.
The patch adds the new trivial helper, mmget_not_zero(), it can have
more users.
Link: http://lkml.kernel.org/r/20160516172254.GA8595@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/sched.h | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 01fe1bb68754..6b3213d96da6 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2723,12 +2723,17 @@ extern struct mm_struct * mm_alloc(void); /* mmdrop drops the mm and the page tables */ extern void __mmdrop(struct mm_struct *); -static inline void mmdrop(struct mm_struct * mm) +static inline void mmdrop(struct mm_struct *mm) { if (unlikely(atomic_dec_and_test(&mm->mm_count))) __mmdrop(mm); } +static inline bool mmget_not_zero(struct mm_struct *mm) +{ + return atomic_inc_not_zero(&mm->mm_users); +} + /* mmput gets rid of the mappings and all user-space */ extern void mmput(struct mm_struct *); /* same as above but performs the slow path from the async kontext. Can |