From: Yang Shi yang.shi@linux.alibaba.com Subject: mm: mempolicy: fix the wrong return value and potential pages leak of mbind
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.
Fix 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.
Link: http://lkml.kernel.org/r/1572454731-3925-1-git-send-email-yang.shi@linux.ali... Fixes: d883544515aa ("mm: mempolicy: make the behavior consistent when MPOL_MF_MOVE* and MPOL_MF_STRICT were specified") Signed-off-by: Yang Shi yang.shi@linux.alibaba.com Reported-by: Li Xinhai lixinhai.lxh@gmail.com Reviewed-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 [4.19 and 5.2+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
mm/mempolicy.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-)
--- a/mm/mempolicy.c~mm-mempolicy-fix-the-wrong-return-value-and-potential-pages-leak-of-mbind +++ a/mm/mempolicy.c @@ -672,7 +672,9 @@ static const struct mm_walk_ops queue_pa * 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 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
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); _