From: Yulei Zhang <yuleixzh...@tencent.com>
Currently dmemfs do not support memory readonly, so change_protection()
will be disabled for dmemfs vma. Since vma->vm_flags could be changed to
new flag in mprotect_fixup(), so we introduce a new vma flag VM_DMEM and
check this flag in mprotect_fixup() to avoid changing vma->vm_flags.
We also check it in vma_to_resize() to disable mremap() for dmemfs vma.
Signed-off-by: Chen Zhuo <sagazc...@tencent.com>
Signed-off-by: Yulei Zhang <yuleixzh...@tencent.com>
---
fs/dmemfs/inode.c | 2 +-
include/linux/mm.h | 7 +++++++
mm/mprotect.c | 5 ++++-
mm/mremap.c | 3 +++
4 files changed, 15 insertions(+), 2 deletions(-)
diff --git a/fs/dmemfs/inode.c b/fs/dmemfs/inode.c
index e37498c00497..b3e394f33b42 100644
--- a/fs/dmemfs/inode.c
+++ b/fs/dmemfs/inode.c
@@ -510,7 +510,7 @@ int dmemfs_file_mmap(struct file *file, struct
vm_area_struct *vma)
if (!(vma->vm_flags & VM_SHARED))
return -EINVAL;
- vma->vm_flags |= VM_PFNMAP;
+ vma->vm_flags |= VM_PFNMAP | VM_DMEM | VM_IO;
file_accessed(file);
vma->vm_ops = &dmemfs_vm_ops;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ca6e6a81576b..7b1e574d2387 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -309,6 +309,8 @@ extern unsigned int kobjsize(const void *objp);
#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
#endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
+#define VM_DMEM BIT(38) /* Dmem page VM */
+
#ifdef CONFIG_ARCH_HAS_PKEYS
# define VM_PKEY_SHIFT VM_HIGH_ARCH_BIT_0
# define VM_PKEY_BIT0 VM_HIGH_ARCH_0 /* A protection key is a 4-bit value */
@@ -656,6 +658,11 @@ static inline bool vma_is_accessible(struct vm_area_struct
*vma)
return vma->vm_flags & VM_ACCESS_FLAGS;
}
+static inline bool vma_is_dmem(struct vm_area_struct *vma)
+{
+ return !!(vma->vm_flags & VM_DMEM);
+}
+
#ifdef CONFIG_SHMEM
/*
* The vma_is_shmem is not inline because it is used only by slow
diff --git a/mm/mprotect.c b/mm/mprotect.c
index ce8b8a5eacbb..36f885cbbb30 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -236,7 +236,7 @@ static inline unsigned long change_pmd_range(struct
vm_area_struct *vma,
* for all the checks.
*/
if (!is_swap_pmd(*pmd) && !pmd_devmap(*pmd) &&
- pmd_none_or_clear_bad_unless_trans_huge(pmd))
+ pmd_none_or_clear_bad_unless_trans_huge(pmd) &&
!pmd_special(*pmd))
goto next;
/* invoke the mmu notifier if the pmd is populated */
@@ -412,6 +412,9 @@ mprotect_fixup(struct vm_area_struct *vma, struct
vm_area_struct **pprev,
return 0;
}
+ if (vma_is_dmem(vma))
+ return -EINVAL;
+
/*
* Do PROT_NONE PFN permission checks here when we can still
* bail out without undoing a lot of state. This is a rather
diff --git a/mm/mremap.c b/mm/mremap.c
index 138abbae4f75..598e68174e24 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -482,6 +482,9 @@ static struct vm_area_struct *vma_to_resize(unsigned long
addr,
if (!vma || vma->vm_start > addr)
return ERR_PTR(-EFAULT);
+ if (vma_is_dmem(vma))
+ return ERR_PTR(-EINVAL);
+
/*
* !old_len is a special case where an attempt is made to 'duplicate'
* a mapping. This makes no sense for private mappings as it will
--
2.28.0
