[PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister()

[rcampbell]

From: Ralph Campbell <rcampb...@nvidia.com>

The helper function hmm_vma_fault() calls hmm_range_register() but is
missing a call to hmm_range_unregister() in one of the error paths.
This leads to a reference count leak and ultimately a memory leak on
struct hmm.

Always call hmm_range_unregister() if hmm_range_register() succeeded.

Signed-off-by: Ralph Campbell <rcampb...@nvidia.com>
Cc: John Hubbard <jhubb...@nvidia.com>
Cc: Ira Weiny <ira.we...@intel.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Cc: Arnd Bergmann <a...@arndb.de>
Cc: Balbir Singh <bsinghar...@gmail.com>
Cc: Dan Carpenter <dan.carpen...@oracle.com>
Cc: Matthew Wilcox <wi...@infradead.org>
Cc: Souptick Joarder <jrdr.li...@gmail.com>
Cc: Andrew Morton <a...@linux-foundation.org>
---
 include/linux/hmm.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index 35a429621e1e..fa0671d67269 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -559,6 +559,7 @@ static inline int hmm_vma_fault(struct hmm_range *range, 
bool block)
                return (int)ret;
 
        if (!hmm_range_wait_until_valid(range, HMM_RANGE_DEFAULT_TIMEOUT)) {
+               hmm_range_unregister(range);
                /*
                 * The mmap_sem was taken by driver we release it here and
                 * returns -EAGAIN which correspond to mmap_sem have been
@@ -570,13 +571,13 @@ static inline int hmm_vma_fault(struct hmm_range *range, 
bool block)
 
        ret = hmm_range_fault(range, block);
        if (ret <= 0) {
+               hmm_range_unregister(range);
                if (ret == -EBUSY || !ret) {
                        /* Same as above, drop mmap_sem to match old API. */
                        up_read(&range->vma->vm_mm->mmap_sem);
                        ret = -EBUSY;
                } else if (ret == -EAGAIN)
                        ret = -EBUSY;
-               hmm_range_unregister(range);
                return ret;
        }
        return 0;
-- 
2.20.1