On 5/7/19 6:15 AM, Souptick Joarder wrote:
On Tue, May 7, 2019 at 5:00 AM <rcampbell@xxxxxxxxxx> wrote:
From: Ralph Campbell <rcampbell@xxxxxxxxxx>
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.
How about * Call hmm_range_unregister() in error path if
hmm_range_register() succeeded* ?
Sure, sounds good.
I'll include that in v2.
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Balbir Singh <bsingharora@xxxxxxxxx>
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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);
what is the reason to moved it up ?
I moved it up because the normal calling pattern is:
down_read(&mm->mmap_sem)
hmm_vma_fault()
hmm_range_register()
hmm_range_fault()
hmm_range_unregister()
up_read(&mm->mmap_sem)
I don't think it is a bug to unlock mmap_sem and then unregister,
it is just more consistent nesting.
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
