diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2016-05-20 16:58:36 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-06-11 12:24:11 +0200 |
| commit | 6ad730b831780ba5532b6cbccc475852400d5e7c (patch) | |
| tree | 0b28c9b3d8e805ec6c78495f6d0b0323daba4e81 /include | |
| parent | 4e06554db5e5c3d693141b84aba3a4f29b7d9ef5 (diff) | |
userfaultfd: don't pin the user memory in userfaultfd_file_create()
commit d2005e3f41d4f9299e2df6a967c8beb5086967a9 upstream.
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>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 a0b540f800d9..315df144c156 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2614,12 +2614,17 @@ 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 *); /* Grab a reference to a task's mm, if it is not already going away */ |