Messages in this thread | | | Subject | Re: [PATCH 4/5] mm/hmm: hmm_vma_fault() doesn't always call hmm_range_unregister() | From | Ralph Campbell <> | Date | Tue, 7 May 2019 11:12:14 -0700 |
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On 5/7/19 6:15 AM, Souptick Joarder wrote: > On Tue, May 7, 2019 at 5:00 AM <rcampbell@nvidia.com> wrote: >> >> From: Ralph Campbell <rcampbell@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. > > 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@nvidia.com> >> Cc: John Hubbard <jhubbard@nvidia.com> >> Cc: Ira Weiny <ira.weiny@intel.com> >> Cc: Dan Williams <dan.j.williams@intel.com> >> Cc: Arnd Bergmann <arnd@arndb.de> >> Cc: Balbir Singh <bsingharora@gmail.com> >> Cc: Dan Carpenter <dan.carpenter@oracle.com> >> Cc: Matthew Wilcox <willy@infradead.org> >> Cc: Souptick Joarder <jrdr.linux@gmail.com> >> Cc: Andrew Morton <akpm@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); > > 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 >>
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