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RDMA/ucontext: Fix regression with disassociate
When this code was consolidated the intention was that the VMA would
become backed by anonymous zero pages after the zap_vma_pte - however this
very subtly relied on setting the vm_ops = NULL and clearing the VM_SHARED
bits to transform the VMA into an anonymous VMA. Since the vm_ops was
removed this broke.
Now userspace gets a SIGBUS if it touches the vma after disassociation.
Instead of converting the VMA to anonymous provide a fault handler that
puts a zero'd page into the VMA when user-space touches it after
disassociation.
Cc: stable@vger.kernel.org
Suggested-by: Andrea Arcangeli <aarcange@redhat.com>
Fixes: 5f9794dc94
("RDMA/ucontext: Add a core API for mmaping driver IO memory")
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
This commit is contained in:
parent
d5e560d3f7
commit
67f269b37f
2 changed files with 50 additions and 3 deletions
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@ -160,6 +160,7 @@ struct ib_uverbs_file {
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struct mutex umap_lock;
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struct list_head umaps;
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struct page *disassociate_page;
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struct idr idr;
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/* spinlock protects write access to idr */
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@ -208,6 +208,9 @@ void ib_uverbs_release_file(struct kref *ref)
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kref_put(&file->async_file->ref,
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ib_uverbs_release_async_event_file);
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put_device(&file->device->dev);
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if (file->disassociate_page)
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__free_pages(file->disassociate_page, 0);
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kfree(file);
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}
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@ -877,9 +880,50 @@ static void rdma_umap_close(struct vm_area_struct *vma)
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kfree(priv);
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}
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/*
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* Once the zap_vma_ptes has been called touches to the VMA will come here and
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* we return a dummy writable zero page for all the pfns.
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*/
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static vm_fault_t rdma_umap_fault(struct vm_fault *vmf)
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{
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struct ib_uverbs_file *ufile = vmf->vma->vm_file->private_data;
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struct rdma_umap_priv *priv = vmf->vma->vm_private_data;
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vm_fault_t ret = 0;
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if (!priv)
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return VM_FAULT_SIGBUS;
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/* Read only pages can just use the system zero page. */
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if (!(vmf->vma->vm_flags & (VM_WRITE | VM_MAYWRITE))) {
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vmf->page = ZERO_PAGE(vmf->vm_start);
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get_page(vmf->page);
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return 0;
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}
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mutex_lock(&ufile->umap_lock);
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if (!ufile->disassociate_page)
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ufile->disassociate_page =
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alloc_pages(vmf->gfp_mask | __GFP_ZERO, 0);
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if (ufile->disassociate_page) {
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/*
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* This VMA is forced to always be shared so this doesn't have
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* to worry about COW.
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*/
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vmf->page = ufile->disassociate_page;
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get_page(vmf->page);
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} else {
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ret = VM_FAULT_SIGBUS;
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}
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mutex_unlock(&ufile->umap_lock);
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return ret;
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}
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static const struct vm_operations_struct rdma_umap_ops = {
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.open = rdma_umap_open,
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.close = rdma_umap_close,
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.fault = rdma_umap_fault,
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};
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static struct rdma_umap_priv *rdma_user_mmap_pre(struct ib_ucontext *ucontext,
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@ -889,6 +933,9 @@ static struct rdma_umap_priv *rdma_user_mmap_pre(struct ib_ucontext *ucontext,
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struct ib_uverbs_file *ufile = ucontext->ufile;
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struct rdma_umap_priv *priv;
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if (!(vma->vm_flags & VM_SHARED))
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return ERR_PTR(-EINVAL);
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if (vma->vm_end - vma->vm_start != size)
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return ERR_PTR(-EINVAL);
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@ -992,7 +1039,7 @@ void uverbs_user_mmap_disassociate(struct ib_uverbs_file *ufile)
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* at a time to get the lock ordering right. Typically there
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* will only be one mm, so no big deal.
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*/
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down_write(&mm->mmap_sem);
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down_read(&mm->mmap_sem);
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mutex_lock(&ufile->umap_lock);
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list_for_each_entry_safe (priv, next_priv, &ufile->umaps,
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list) {
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@ -1004,10 +1051,9 @@ void uverbs_user_mmap_disassociate(struct ib_uverbs_file *ufile)
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zap_vma_ptes(vma, vma->vm_start,
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vma->vm_end - vma->vm_start);
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vma->vm_flags &= ~(VM_SHARED | VM_MAYSHARE);
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}
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mutex_unlock(&ufile->umap_lock);
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up_write(&mm->mmap_sem);
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up_read(&mm->mmap_sem);
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mmput(mm);
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}
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}
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