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userfaultfd_zeropage: return -ENOSPC in case mm has gone 

In the non-cooperative userfaultfd case, the process exit may race with
outstanding mcopy_atomic called by the uffd monitor.  Returning -ENOSPC
instead of -EINVAL when mm is already gone will allow uffd monitor to
distinguish this case from other error conditions.

Unfortunately I overlooked userfaultfd_zeropage when updating
userfaultd_copy().

Link: http://lkml.kernel.org/r/1501136819-21857-1-git-send-email-rppt@linux.vnet.ibm.com
Fixes: 96333187ab ("userfaultfd_copy: return -ENOSPC in case mm has gone")
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mike Rapoport 2017-08-02 13:32:15 -07:00 committed by Linus Torvalds
parent 167d0f258f
commit 9d95aa4bad
1 changed files with 2 additions and 0 deletions
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2
fs/userfaultfd.c
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@ -1643,6 +1643,8 @@ static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
uffdio_zeropage.range.len);
mmput(ctx->mm);
} else {
return -ENOSPC;
}
if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
return -EFAULT;