From: Brian Geffon <bgeffon@xxxxxxxxxx> Subject: Revert "mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio" 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 Link: https://lkml.kernel.org/r/20210323182520.2712101-2-bgeffon@xxxxxxxxxx Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx> Acked-by: Hugh Dickins <hughd@xxxxxxxxxx> Reviewed-by: Dmitry Safonov <0x7f454c46@xxxxxxxxx> Cc: Alejandro Colomar <alx.manpages@xxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill@xxxxxxxxxxxxx> Cc: Lokesh Gidra <lokeshgidra@xxxxxxxxxx> Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx> Cc: "Michael S . Tsirkin" <mst@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Sonny Rao <sonnyrao@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/cpu/resctrl/pseudo_lock.c | 2 +- fs/aio.c | 5 +---- include/linux/mm.h | 2 +- mm/mmap.c | 6 +----- mm/mremap.c | 2 +- 5 files changed, 5 insertions(+), 12 deletions(-) --- a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c~revert-mremap-dont-allow-mremap_dontunmap-on-special_mappings-and-aio +++ a/arch/x86/kernel/cpu/resctrl/pseudo_lock.c @@ -1458,7 +1458,7 @@ static int pseudo_lock_dev_release(struc 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; --- a/fs/aio.c~revert-mremap-dont-allow-mremap_dontunmap-on-special_mappings-and-aio +++ a/fs/aio.c @@ -323,16 +323,13 @@ static void aio_free_ring(struct kioctx } } -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); --- a/include/linux/mm.h~revert-mremap-dont-allow-mremap_dontunmap-on-special_mappings-and-aio +++ a/include/linux/mm.h @@ -580,7 +580,7 @@ struct vm_operations_struct { void (*close)(struct vm_area_struct * area); /* Called any time before splitting to check if it's allowed */ int (*may_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); /* * Called by mprotect() to make driver-specific permission * checks before mprotect() is finalised. The VMA must not --- a/mm/mmap.c~revert-mremap-dont-allow-mremap_dontunmap-on-special_mappings-and-aio +++ a/mm/mmap.c @@ -3409,14 +3409,10 @@ static const char *special_mapping_name( 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; --- a/mm/mremap.c~revert-mremap-dont-allow-mremap_dontunmap-on-special_mappings-and-aio +++ a/mm/mremap.c @@ -545,7 +545,7 @@ static unsigned long move_vma(struct vm_ 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)) { _
