Messages in this thread | | | Subject | Re: [PATCH] mm: mempolicy: fix the wrong return value and potential pages leak of mbind | From | Yang Shi <> | Date | Wed, 30 Oct 2019 11:14:58 -0700 |
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On 10/30/19 9:58 AM, Yang Shi wrote: > The commit d883544515aa ("mm: mempolicy: make the behavior consistent > when MPOL_MF_MOVE* and MPOL_MF_STRICT were specified") fixed the return > value of mbind() for a couple of corner cases. But, it altered the > errno for some other cases, for example, mbind() should return -EFAULT > when part or all of the memory range specified by nodemask and maxnode > points outside your accessible address space, or there was an unmapped > hole in the specified memory range specified by addr and len. > > Fixed this by preserving the errno returned by queue_pages_range(). > And, the pagelist may be not empty even though queue_pages_range() > returns error, put the pages back to LRU since mbind_range() is not called > to really apply the policy so those pages should not be migrated, this > is also the old behavior before the problematic commit. Forgot fixes tag.
Fixes: d883544515aa ("mm: mempolicy: make the behavior consistent when MPOL_MF_MOVE* and MPOL_MF_STRICT were specified")
> Reported-by: Li Xinhai <lixinhai.lxh@gmail.com> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Mel Gorman <mgorman@techsingularity.net> > Cc: <stable@vger.kernel.org> v4.19 and v5.2+ > Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com> > --- > mm/mempolicy.c | 14 +++++++++----- > 1 file changed, 9 insertions(+), 5 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 4ae967b..e08c941 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -672,7 +672,9 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, > * 1 - there is unmovable page, but MPOL_MF_MOVE* & MPOL_MF_STRICT were > * specified. > * 0 - queue pages successfully or no misplaced page. > - * -EIO - there is misplaced page and only MPOL_MF_STRICT was specified. > + * errno - i.e. misplaced pages with MPOL_MF_STRICT specified (-EIO) or > + * memory range specified by nodemask and maxnode points outside > + * your accessible address space (-EFAULT) > */ > static int > queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end, > @@ -1286,7 +1288,7 @@ static long do_mbind(unsigned long start, unsigned long len, > flags | MPOL_MF_INVERT, &pagelist); > > if (ret < 0) { > - err = -EIO; > + err = ret; > goto up_out; > } > > @@ -1305,10 +1307,12 @@ static long do_mbind(unsigned long start, unsigned long len, > > if ((ret > 0) || (nr_failed && (flags & MPOL_MF_STRICT))) > err = -EIO; > - } else > - putback_movable_pages(&pagelist); > - > + } else { > up_out: > + if (!list_empty(&pagelist)) > + putback_movable_pages(&pagelist); > + } > + > up_write(&mm->mmap_sem); > mpol_out: > mpol_put(new);
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