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SubjectRe: [akpm-mm:mm-unstable 284/293] mm/khugepaged.c:2409 madvise_collapse() warn: possible memory leak of 'cc'
On Jul 12 10:02, Yang Shi wrote:
> On Tue, Jul 12, 2022 at 5:36 AM Dan Carpenter <dan.carpenter@oracle.com> wrote:
> >
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable
> > head: 0e9f775fb0b4adf1a4ef50ea156ead09a0fc5194
> > commit: 9f626ffb1d1c5c26b4a8e0fdffec784a5f773274 [284/293] mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse
> > config: i386-randconfig-m021 (https://download.01.org/0day-ci/archive/20220710/202207100715.TBIYQ4fc-lkp@intel.com/config)
> > compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
> >
> > If you fix the issue, kindly add following tag where applicable
> > Reported-by: kernel test robot <lkp@intel.com>
> > Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> >
> > smatch warnings:
> > mm/khugepaged.c:2409 madvise_collapse() warn: possible memory leak of 'cc'
> >
> > vim +/cc +2409 mm/khugepaged.c
> >
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2387 int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2388 unsigned long start, unsigned long end)
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2389 {
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2390 struct collapse_control *cc;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2391 struct mm_struct *mm = vma->vm_mm;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2392 unsigned long hstart, hend, addr;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2393 int thps = 0, last_fail = SCAN_FAIL;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2394 bool mmap_locked = true;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2395
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2396 BUG_ON(vma->vm_start > start);
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2397 BUG_ON(vma->vm_end < end);
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2398
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2399 cc = kmalloc(sizeof(*cc), GFP_KERNEL);
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2400 if (!cc)
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2401 return -ENOMEM;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2402 cc->is_khugepaged = false;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2403 cc->last_target_node = NUMA_NO_NODE;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2404
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2405 *prev = vma;
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2406
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2407 /* TODO: Support file/shmem */
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 2408 if (!vma->anon_vma || !vma_is_anonymous(vma))
> > 9f626ffb1d1c5c Zach O'Keefe 2022-07-06 @2409 return -EINVAL;
>
> It seems better to move the cc kmalloc after the anonymous vma check?
>

Agreed - something I only noticed when fixing this. I've cleaned up some
ordering here, now looks like:

---8<---
BUG_ON(vma->vm_start > start);
BUG_ON(vma->vm_end < end);

*prev = vma;

/* TODO: Support file/shmem */
if (!vma->anon_vma || !vma_is_anonymous(vma))
return -EINVAL;

if (!hugepage_vma_check(vma, vma->vm_flags, false, false, false))
return -EINVAL;

cc = kmalloc(sizeof(*cc), GFP_KERNEL);
if (!cc)
return -ENOMEM;
cc->is_khugepaged = false;
cc->last_target_node = NUMA_NO_NODE;

mmgrab(mm);
lru_add_drain_all();

hstart = (start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = end & HPAGE_PMD_MASK;

for (addr = hstart; addr < hend; addr += HPAGE_PMD_SIZE) {
---8<---
out_nolock:
mmap_assert_locked(mm);
mmdrop(mm);
kfree(cc);
---8<---

> >
> > kfree(cc);?
> >
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://01.org/lkp
> >
> >

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