FAILED: patch "[PATCH] s390/pci_mmio: fully validate the VMA before calling" failed to apply to 5.4-stable tree

FAILED: patch "[PATCH] s390/pci_mmio: fully validate the VMA before calling" failed to apply to 5.4-stable tree

[gregkh]

The patch below does not apply to the 5.4-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)))

[PATCH 5.4 STABLE] s390/pci_mmio: fully validate the VMA before calling follow_pte()

[David Hildenbrand]

commit a8b92b8c1eac8d655a97b1e90f4d83c25d9b9a18 upstream.

Note: We don't have vma_lookup() in the 5.4-stable tree, so perform the VMA
check manually.

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>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 arch/s390/pci/pci_mmio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/pci/pci_mmio.c b/arch/s390/pci/pci_mmio.c
index 020a2c514d96..921f0fc12f1f 100644
--- a/arch/s390/pci/pci_mmio.c
+++ b/arch/s390/pci/pci_mmio.c
@@ -128,7 +128,7 @@ static long get_pfn(unsigned long user_addr, unsigned long access,
 	down_read(&current->mm->mmap_sem);
 	ret = -EINVAL;
 	vma = find_vma(current->mm, user_addr);
-	if (!vma)
+	if (!vma || user_addr < vma->vm_start)
 		goto out;
 	ret = -EACCES;
 	if (!(vma->vm_flags & access))
-- 
2.31.1