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Set VM_DONTEXPAND on guest_memfd VMAs. In addition, this disables khugepaged from operating on guest_memfd folios, which may result in unintended merging of guest_memfd folios. Change-Id: I5867edcb66b075b54b25260afd22a198aee76df1 Signed-off-by: Ackerley Tng Reported-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com Tested-by: syzbot+33a04338019ac7e43a44@syzkaller.appspotmail.com --- virt/kvm/guest_memfd.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index fdaea3422c30..3d4ac461c28b 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -480,6 +480,12 @@ static int kvm_gmem_mmap(struct file *file, struct vm_= area_struct *vma) return -EINVAL; } + /* + * Disable VMA merging - guest_memfd VMAs should be + * static. This also stops khugepaged from operating on + * guest_memfd VMAs and folios. + */ + vm_flags_set(vma, VM_DONTEXPAND); vma->vm_ops =3D &kvm_gmem_vm_ops; return 0; -- 2.53.0.rc2.204.g2597b5adb4-goog