The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From a8b92b8c1eac8d655a97b1e90f4d83c25d9b9a18 Mon Sep 17 00:00:00 2001

From: David Hildenbrand david@redhat.com Date: Thu, 9 Sep 2021 16:59:42 +0200 Subject: [PATCH] s390/pci_mmio: fully validate the VMA before calling follow_pte()

We should not walk/touch page tables outside of VMA boundaries when holding only the mmap sem in read mode. Evil user space can modify the VMA layout just before this function runs and e.g., trigger races with page table removal code since commit dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap").

find_vma() does not check if the address is >= the VMA start address; use vma_lookup() instead.

Reviewed-by: Niklas Schnelle schnelle@linux.ibm.com Reviewed-by: Liam R. Howlett Liam.Howlett@oracle.com Fixes: dd2283f2605e ("mm: mmap: zap pages with read mmap_sem in munmap") Signed-off-by: David Hildenbrand david@redhat.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com

diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c index ae683aa623ac..c5b35ea129cf 100644 --- a/arch/s390/pci/pci_mmio.c +++ b/arch/s390/pci/pci_mmio.c @@ -159,7 +159,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_write, unsigned long, mmio_addr,

mmap_read_lock(current->mm); ret = -EINVAL; - vma = find_vma(current->mm, mmio_addr); + vma = vma_lookup(current->mm, mmio_addr); if (!vma) goto out_unlock_mmap; if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) @@ -298,7 +298,7 @@ SYSCALL_DEFINE3(s390_pci_mmio_read, unsigned long, mmio_addr,

mmap_read_lock(current->mm); ret = -EINVAL; - vma = find_vma(current->mm, mmio_addr); + vma = vma_lookup(current->mm, mmio_addr); if (!vma) goto out_unlock_mmap; if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))