From: Li Xinhai lixinhai.lxh@gmail.com
mainline inclusion from mainline-v5.5-rc1 commit a18b3ac25bb7be4781cb9e6d31f3e57b3ba01b06 category: bugfix bugzilla: 97909 CVE: NA
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Patch series "mm: Fix checking unmapped holes for mbind", v4.
This patchset fix checking unmapped holes for mbind().
First patch makes sure the vma been correctly tracked in .test_walk(), so each time when .test_walk() is called, the neighborhood of two vma is correct.
Current problem is that the !vma_migratable() check could cause return immediately without update tracking to vma.
Second patch fix the inconsistent report of EFAULT when mbind() is called for MPOL_DEFAULT and non MPOL_DEFAULT cases, so application do not need to have workaround code to handle this special behavior. Currently there are two problems, one is that the .test_walk() can not know there is hole at tail side of range, because .test_walk() only call for vma not for hole. The other one is that mbind_range() checks for hole at head side of range but do not consider the MPOL_MF_DISCONTIG_OK flag as done in .test_walk().
This patch (of 2):
Checking unmapped hole and updating the previous vma must be handled first, otherwise the unmapped hole could be calculated from a wrong previous vma.
Several commits were relevant to this error:
- commit 6f4576e3687b ("mempolicy: apply page table walker on queue_pages_range()")
This commit was correct, the VM_PFNMAP check was after updating previous vma
- commit 48684a65b4e3 ("mm: pagewalk: fix misbehavior of walk_page_range for vma(VM_PFNMAP)")
This commit added VM_PFNMAP check before updating previous vma. Then, there were two VM_PFNMAP check did same thing twice.
- commit acda0c334028 ("mm/mempolicy.c: get rid of duplicated check for vma(VM_PFNMAP) in queue_page s_range()")
This commit tried to fix the duplicated VM_PFNMAP check, but it wrongly removed the one which was after updating vma.
Link: http://lkml.kernel.org/r/1573218104-11021-2-git-send-email-lixinhai.lxh@gmai... Fixes: acda0c334028 (mm/mempolicy.c: get rid of duplicated check for vma(VM_PFNMAP) in queue_pages_range()) Signed-off-by: Li Xinhai lixinhai.lxh@gmail.com Reviewed-by: Naoya Horiguchi n-horiguchi@ah.jp.nec.com Cc: Michal Hocko mhocko@suse.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Hugh Dickins hughd@google.com Cc: linux-man linux-man@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Nanyong Sun sunnanyong@huawei.com Reviewed-by: tong tiangen tongtiangen@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- mm/mempolicy.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 3a835f96c8fea..7b4ba2f355911 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -657,6 +657,16 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, unsigned long endvma = vma->vm_end; unsigned long flags = qp->flags;
+ /* range check first */ + if (!(flags & MPOL_MF_DISCONTIG_OK)) { + if (!vma->vm_next && vma->vm_end < end) + return -EFAULT; + if (qp->prev && qp->prev->vm_end < vma->vm_start) + return -EFAULT; + } + + qp->prev = vma; + /* * Need check MPOL_MF_STRICT to return -EIO if possible * regardless of vma_migratable @@ -670,15 +680,6 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end, if (vma->vm_start > start) start = vma->vm_start;
- if (!(flags & MPOL_MF_DISCONTIG_OK)) { - if (!vma->vm_next && vma->vm_end < end) - return -EFAULT; - if (qp->prev && qp->prev->vm_end < vma->vm_start) - return -EFAULT; - } - - qp->prev = vma; - if (flags & MPOL_MF_LAZY) { /* Similar to task_numa_work, skip inaccessible VMAs */ if (!is_vm_hugetlb_page(vma) &&