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BACKPORT: FROMLIST: Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio"

Browse source 
This reverts commit cd544fd1dc9293c6702fab6effa63dac1cc67e99.

As discussed in [1] this commit was a no-op because the mapping type was
checked in vma_to_resize before move_vma is ever called. This meant that
vm_ops->mremap() would never be called on such mappings. Furthermore,
we've since expanded support of MREMAP_DONTUNMAP to non-anonymous
mappings, and these special mappings are still protected by the existing
check of !VM_DONTEXPAND and !VM_PFNMAP which will result in a -EINVAL.

1. https://lkml.org/lkml/2020/12/28/2340

Signed-off-by: Brian Geffon <bgeffon@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Dmitry Safonov <0x7f454c46@gmail.com>

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Link: https://lore.kernel.org/patchwork/patch/1401226/
Conflicts: include/linux/mm.h
(Resolved minor conflict with manual rebase)
Bug: 160737021
Bug: 169683130
Change-Id: I97d29e6a54cee07ba69d6bb880778ee1fea8ff7c
This commit is contained in:
Brian Geffon 2021-03-23 11:25:18 -07:00 • committed by Michael Bestas
commit 2af548dd44
5 changed files with 5 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

2
arch/x86/kernel/cpu/resctrl/pseudo_lock.c
View file

@ -1464,7 +1464,7 @@ static int pseudo_lock_dev_release(struct inode *inode, struct file *filp)
return 0;
}
static int pseudo_lock_dev_mremap(struct vm_area_struct *area, unsigned long flags)
static int pseudo_lock_dev_mremap(struct vm_area_struct *area)
{
/* Not supported */
return -EINVAL;

5
fs/aio.c
View file

@ -320,16 +320,13 @@ static void aio_free_ring(struct kioctx *ctx)
}
}
static int aio_ring_mremap(struct vm_area_struct *vma, unsigned long flags)
static int aio_ring_mremap(struct vm_area_struct *vma)
{
struct file *file = vma->vm_file;
struct mm_struct *mm = vma->vm_mm;
struct kioctx_table *table;
int i, res = -EINVAL;
if (flags & MREMAP_DONTUNMAP)
return -EINVAL;
spin_lock(&mm->ioctx_lock);
rcu_read_lock();
table = rcu_dereference(mm->ioctx_table);

2
include/linux/mm.h
View file

@ -499,7 +499,7 @@ struct vm_operations_struct {
void (*open)(struct vm_area_struct * area);
void (*close)(struct vm_area_struct * area);
int (*split)(struct vm_area_struct * area, unsigned long addr);
int (*mremap)(struct vm_area_struct *area, unsigned long flags);
int (*mremap)(struct vm_area_struct *area);
vm_fault_t (*fault)(struct vm_fault *vmf);
vm_fault_t (*huge_fault)(struct vm_fault *vmf,
enum page_entry_size pe_size);

6
mm/mmap.c
View file

@ -3492,14 +3492,10 @@ static const char *special_mapping_name(struct vm_area_struct *vma)
return ((struct vm_special_mapping *)vma->vm_private_data)->name;
}
static int special_mapping_mremap(struct vm_area_struct *new_vma,
unsigned long flags)
static int special_mapping_mremap(struct vm_area_struct *new_vma)
{
struct vm_special_mapping *sm = new_vma->vm_private_data;
if (flags & MREMAP_DONTUNMAP)
return -EINVAL;
if (WARN_ON_ONCE(current->mm != new_vma->vm_mm))
return -EFAULT;

2
mm/mremap.c
View file

@ -577,7 +577,7 @@ static unsigned long move_vma(struct vm_area_struct *vma,
if (moved_len < old_len) {
err = -ENOMEM;
} else if (vma->vm_ops && vma->vm_ops->mremap) {
err = vma->vm_ops->mremap(new_vma, flags);
err = vma->vm_ops->mremap(new_vma);
}
if (unlikely(err)) {