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mm/mremap: move remap_is_valid() into check_prep_vma()
Group parameter check logic together, moving check_mremap_params() next to it. This puts all such checks into a single place, and invokes them early so we can simply bail out as soon as we are aware that a condition is not met. No functional change intended. Link: https://lkml.kernel.org/r/4d0669c23531629d8ead42aa701c6237bd6bf012.1752770784.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Vlastimil Babka <vbabka@suse.cz> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christian Brauner <brauner@kernel.org> Cc: Jan Kara <jack@suse.cz> Cc: Jann Horn <jannh@google.com> Cc: Liam Howlett <liam.howlett@oracle.com> Cc: Peter Xu <peterx@redhat.com> Cc: Rik van Riel <riel@surriel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes
Andrew Morton
parent
a85dc37186
commit
9b2301bf8d
289
mm/mremap.c
289
mm/mremap.c
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@ -1306,71 +1306,6 @@ static unsigned long move_vma(struct vma_remap_struct *vrm)
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return err ? (unsigned long)err : vrm->new_addr;
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}
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/*
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* remap_is_valid() - Ensure the VMA can be moved or resized to the new length,
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* at the given address.
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*
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* Return 0 on success, error otherwise.
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*/
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static int remap_is_valid(struct vma_remap_struct *vrm)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma = vrm->vma;
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unsigned long addr = vrm->addr;
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unsigned long old_len = vrm->old_len;
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unsigned long new_len = vrm->new_len;
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unsigned long pgoff;
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/*
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* !old_len is a special case where an attempt is made to 'duplicate'
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* a mapping. This makes no sense for private mappings as it will
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* instead create a fresh/new mapping unrelated to the original. This
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* is contrary to the basic idea of mremap which creates new mappings
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* based on the original. There are no known use cases for this
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* behavior. As a result, fail such attempts.
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*/
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if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
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pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n",
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current->comm, current->pid);
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return -EINVAL;
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}
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if ((vrm->flags & MREMAP_DONTUNMAP) &&
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(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
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return -EINVAL;
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/*
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* We permit crossing of boundaries for the range being unmapped due to
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* a shrink.
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*/
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if (vrm->remap_type == MREMAP_SHRINK)
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old_len = new_len;
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/* We can't remap across vm area boundaries */
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if (old_len > vma->vm_end - addr)
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return -EFAULT;
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if (new_len == old_len)
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return 0;
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/* Need to be careful about a growing mapping */
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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return -EINVAL;
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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return -EFAULT;
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if (!mlock_future_ok(mm, vma->vm_flags, vrm->delta))
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return -EAGAIN;
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if (!may_expand_vm(mm, vma->vm_flags, vrm->delta >> PAGE_SHIFT))
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return -ENOMEM;
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return 0;
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}
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/*
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* The user has requested that the VMA be shrunk (i.e., old_len > new_len), so
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* execute this, optionally dropping the mmap lock when we do so.
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@ -1497,77 +1432,6 @@ static bool vrm_can_expand_in_place(struct vma_remap_struct *vrm)
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return true;
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}
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/*
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* Are the parameters passed to mremap() valid? If so return 0, otherwise return
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* error.
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*/
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static unsigned long check_mremap_params(struct vma_remap_struct *vrm)
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{
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unsigned long addr = vrm->addr;
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unsigned long flags = vrm->flags;
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/* Ensure no unexpected flag values. */
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if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
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return -EINVAL;
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/* Start address must be page-aligned. */
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if (offset_in_page(addr))
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return -EINVAL;
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/*
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* We allow a zero old-len as a special case
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* for DOS-emu "duplicate shm area" thing. But
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* a zero new-len is nonsensical.
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*/
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if (!vrm->new_len)
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return -EINVAL;
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/* Is the new length or address silly? */
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if (vrm->new_len > TASK_SIZE ||
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vrm->new_addr > TASK_SIZE - vrm->new_len)
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return -EINVAL;
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/* Remainder of checks are for cases with specific new_addr. */
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if (!vrm_implies_new_addr(vrm))
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return 0;
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/* The new address must be page-aligned. */
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if (offset_in_page(vrm->new_addr))
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return -EINVAL;
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/* A fixed address implies a move. */
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if (!(flags & MREMAP_MAYMOVE))
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return -EINVAL;
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/* MREMAP_DONTUNMAP does not allow resizing in the process. */
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if (flags & MREMAP_DONTUNMAP && vrm->old_len != vrm->new_len)
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return -EINVAL;
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/* Target VMA must not overlap source VMA. */
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if (vrm_overlaps(vrm))
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return -EINVAL;
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/*
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* move_vma() need us to stay 4 maps below the threshold, otherwise
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* it will bail out at the very beginning.
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* That is a problem if we have already unmaped the regions here
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* (new_addr, and old_addr), because userspace will not know the
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* state of the vma's after it gets -ENOMEM.
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* So, to avoid such scenario we can pre-compute if the whole
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* operation has high chances to success map-wise.
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* Worst-scenario case is when both vma's (new_addr and old_addr) get
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* split in 3 before unmapping it.
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* That means 2 more maps (1 for each) to the ones we already hold.
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* Check whether current map count plus 2 still leads us to 4 maps below
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* the threshold, otherwise return -ENOMEM here to be more safe.
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*/
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if ((current->mm->map_count + 2) >= sysctl_max_map_count - 3)
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return -ENOMEM;
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return 0;
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}
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/*
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* We know we can expand the VMA in-place by delta pages, so do so.
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*
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@ -1719,9 +1583,26 @@ static bool vrm_will_map_new(struct vma_remap_struct *vrm)
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return false;
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}
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static void notify_uffd(struct vma_remap_struct *vrm, bool failed)
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{
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struct mm_struct *mm = current->mm;
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/* Regardless of success/failure, we always notify of any unmaps. */
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userfaultfd_unmap_complete(mm, vrm->uf_unmap_early);
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if (failed)
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mremap_userfaultfd_fail(vrm->uf);
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else
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mremap_userfaultfd_complete(vrm->uf, vrm->addr,
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vrm->new_addr, vrm->old_len);
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userfaultfd_unmap_complete(mm, vrm->uf_unmap);
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}
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static int check_prep_vma(struct vma_remap_struct *vrm)
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{
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struct vm_area_struct *vma = vrm->vma;
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struct mm_struct *mm = current->mm;
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unsigned long addr = vrm->addr;
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unsigned long old_len, new_len, pgoff;
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if (!vma)
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return -EFAULT;
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@ -1738,26 +1619,134 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
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vrm->remap_type = vrm_remap_type(vrm);
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/* For convenience, we set new_addr even if VMA won't move. */
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if (!vrm_implies_new_addr(vrm))
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vrm->new_addr = vrm->addr;
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vrm->new_addr = addr;
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if (vrm_will_map_new(vrm))
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return remap_is_valid(vrm);
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/* Below only meaningful if we expand or move a VMA. */
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if (!vrm_will_map_new(vrm))
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return 0;
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old_len = vrm->old_len;
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new_len = vrm->new_len;
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/*
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* !old_len is a special case where an attempt is made to 'duplicate'
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* a mapping. This makes no sense for private mappings as it will
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* instead create a fresh/new mapping unrelated to the original. This
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* is contrary to the basic idea of mremap which creates new mappings
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* based on the original. There are no known use cases for this
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* behavior. As a result, fail such attempts.
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*/
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if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
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pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap. This is not supported.\n",
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current->comm, current->pid);
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return -EINVAL;
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}
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if ((vrm->flags & MREMAP_DONTUNMAP) &&
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(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
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return -EINVAL;
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/*
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* We permit crossing of boundaries for the range being unmapped due to
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* a shrink.
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*/
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if (vrm->remap_type == MREMAP_SHRINK)
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old_len = new_len;
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/* We can't remap across vm area boundaries */
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if (old_len > vma->vm_end - addr)
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return -EFAULT;
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if (new_len == old_len)
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return 0;
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/* Need to be careful about a growing mapping */
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pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
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pgoff += vma->vm_pgoff;
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if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
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return -EINVAL;
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if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
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return -EFAULT;
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if (!mlock_future_ok(mm, vma->vm_flags, vrm->delta))
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return -EAGAIN;
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if (!may_expand_vm(mm, vma->vm_flags, vrm->delta >> PAGE_SHIFT))
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return -ENOMEM;
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return 0;
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}
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static void notify_uffd(struct vma_remap_struct *vrm, bool failed)
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{
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struct mm_struct *mm = current->mm;
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/*
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* Are the parameters passed to mremap() valid? If so return 0, otherwise return
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* error.
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*/
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static unsigned long check_mremap_params(struct vma_remap_struct *vrm)
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/* Regardless of success/failure, we always notify of any unmaps. */
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userfaultfd_unmap_complete(mm, vrm->uf_unmap_early);
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if (failed)
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mremap_userfaultfd_fail(vrm->uf);
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else
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mremap_userfaultfd_complete(vrm->uf, vrm->addr,
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vrm->new_addr, vrm->old_len);
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userfaultfd_unmap_complete(mm, vrm->uf_unmap);
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{
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unsigned long addr = vrm->addr;
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unsigned long flags = vrm->flags;
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/* Ensure no unexpected flag values. */
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if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE | MREMAP_DONTUNMAP))
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return -EINVAL;
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/* Start address must be page-aligned. */
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if (offset_in_page(addr))
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return -EINVAL;
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/*
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* We allow a zero old-len as a special case
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* for DOS-emu "duplicate shm area" thing. But
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* a zero new-len is nonsensical.
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*/
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if (!vrm->new_len)
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return -EINVAL;
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/* Is the new length or address silly? */
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if (vrm->new_len > TASK_SIZE ||
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vrm->new_addr > TASK_SIZE - vrm->new_len)
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return -EINVAL;
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/* Remainder of checks are for cases with specific new_addr. */
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if (!vrm_implies_new_addr(vrm))
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return 0;
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/* The new address must be page-aligned. */
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if (offset_in_page(vrm->new_addr))
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return -EINVAL;
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/* A fixed address implies a move. */
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if (!(flags & MREMAP_MAYMOVE))
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return -EINVAL;
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/* MREMAP_DONTUNMAP does not allow resizing in the process. */
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if (flags & MREMAP_DONTUNMAP && vrm->old_len != vrm->new_len)
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return -EINVAL;
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/* Target VMA must not overlap source VMA. */
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if (vrm_overlaps(vrm))
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return -EINVAL;
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/*
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* move_vma() need us to stay 4 maps below the threshold, otherwise
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* it will bail out at the very beginning.
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* That is a problem if we have already unmaped the regions here
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* (new_addr, and old_addr), because userspace will not know the
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* state of the vma's after it gets -ENOMEM.
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* So, to avoid such scenario we can pre-compute if the whole
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* operation has high chances to success map-wise.
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* Worst-scenario case is when both vma's (new_addr and old_addr) get
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* split in 3 before unmapping it.
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* That means 2 more maps (1 for each) to the ones we already hold.
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* Check whether current map count plus 2 still leads us to 4 maps below
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* the threshold, otherwise return -ENOMEM here to be more safe.
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*/
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if ((current->mm->map_count + 2) >= sysctl_max_map_count - 3)
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return -ENOMEM;
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return 0;
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}
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static unsigned long do_mremap(struct vma_remap_struct *vrm)
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