[PATCH kernel v6 6/7] vfio/spapr: Reference mm in tce_container
David Gibson
david at gibson.dropbear.id.au
Tue Nov 29 15:55:23 AEDT 2016
On Thu, Nov 24, 2016 at 04:48:09PM +1100, Alexey Kardashevskiy wrote:
> In some situations the userspace memory context may live longer than
> the userspace process itself so if we need to do proper memory context
> cleanup, we better have tce_container take a reference to mm_struct and
> use it later when the process is gone (@current or @current->mm is NULL).
>
> This references mm and stores the pointer in the container; this is done
> in a new helper - tce_iommu_mm_set() - when one of the following happens:
> - a container is enabled (IOMMU v1);
> - a first attempt to pre-register memory is made (IOMMU v2);
> - a DMA window is created (IOMMU v2).
> The @mm stays referenced till the container is destroyed.
>
> This replaces current->mm with container->mm everywhere except debug
> prints.
>
> This adds a check that current->mm is the same as the one stored in
> the container to prevent userspace from making changes to a memory
> context of other processes.
>
> DMA map/unmap ioctls() do not check for @mm as they already check
> for @enabled which is set after tce_iommu_mm_set() is called.
>
> This does not reference a task as multiple threads within the same mm
> are allowed to ioctl() to vfio and supposedly they will have same limits
> and capabilities and if they do not, we'll just fail with no harm made.
>
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
> ---
> Changes:
> v6:
> * updated the commit log about not referencing task
>
> v5:
> * postpone referencing of mm
>
> v4:
> * added check for container->mm!=current->mm in tce_iommu_ioctl()
> for all ioctls and removed other redundand checks
> ---
> drivers/vfio/vfio_iommu_spapr_tce.c | 159 ++++++++++++++++++++++--------------
> 1 file changed, 99 insertions(+), 60 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index 88622be..b2fb05ac 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -31,49 +31,49 @@
> static void tce_iommu_detach_group(void *iommu_data,
> struct iommu_group *iommu_group);
>
> -static long try_increment_locked_vm(long npages)
> +static long try_increment_locked_vm(struct mm_struct *mm, long npages)
> {
> long ret = 0, locked, lock_limit;
>
> - if (!current || !current->mm)
> - return -ESRCH; /* process exited */
> + if (!mm)
> + return -EPERM;
Can this happen in practice, or should it be a WARN_ON?
>
> if (!npages)
> return 0;
>
> - down_write(¤t->mm->mmap_sem);
> - locked = current->mm->locked_vm + npages;
> + down_write(&mm->mmap_sem);
> + locked = mm->locked_vm + npages;
> lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> if (locked > lock_limit && !capable(CAP_IPC_LOCK))
> ret = -ENOMEM;
> else
> - current->mm->locked_vm += npages;
> + mm->locked_vm += npages;
>
> pr_debug("[%d] RLIMIT_MEMLOCK +%ld %ld/%ld%s\n", current->pid,
> npages << PAGE_SHIFT,
> - current->mm->locked_vm << PAGE_SHIFT,
> + mm->locked_vm << PAGE_SHIFT,
> rlimit(RLIMIT_MEMLOCK),
> ret ? " - exceeded" : "");
>
> - up_write(¤t->mm->mmap_sem);
> + up_write(&mm->mmap_sem);
>
> return ret;
> }
>
> -static void decrement_locked_vm(long npages)
> +static void decrement_locked_vm(struct mm_struct *mm, long npages)
> {
> - if (!current || !current->mm || !npages)
> - return; /* process exited */
> + if (!mm && !npages)
Do you mean &&, or ||?
> + return;
>
> - down_write(¤t->mm->mmap_sem);
> - if (WARN_ON_ONCE(npages > current->mm->locked_vm))
> - npages = current->mm->locked_vm;
> - current->mm->locked_vm -= npages;
> + down_write(&mm->mmap_sem);
> + if (WARN_ON_ONCE(npages > mm->locked_vm))
> + npages = mm->locked_vm;
> + mm->locked_vm -= npages;
> pr_debug("[%d] RLIMIT_MEMLOCK -%ld %ld/%ld\n", current->pid,
> npages << PAGE_SHIFT,
> - current->mm->locked_vm << PAGE_SHIFT,
> + mm->locked_vm << PAGE_SHIFT,
> rlimit(RLIMIT_MEMLOCK));
> - up_write(¤t->mm->mmap_sem);
> + up_write(&mm->mmap_sem);
> }
>
> /*
> @@ -99,26 +99,38 @@ struct tce_container {
> bool v2;
> bool def_window_pending;
> unsigned long locked_pages;
> + struct mm_struct *mm;
> struct iommu_table *tables[IOMMU_TABLE_GROUP_MAX_TABLES];
> struct list_head group_list;
> };
>
> +static long tce_iommu_mm_set(struct tce_container *container)
> +{
> + if (container->mm) {
> + if (container->mm == current->mm)
> + return 0;
> + return -EPERM;
> + }
> + BUG_ON(!current->mm);
> + container->mm = current->mm;
> + atomic_inc(&container->mm->mm_count);
> +
> + return 0;
> +}
> +
> static long tce_iommu_unregister_pages(struct tce_container *container,
> __u64 vaddr, __u64 size)
> {
> struct mm_iommu_table_group_mem_t *mem;
>
> - if (!current || !current->mm)
> - return -ESRCH; /* process exited */
> -
> if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
> return -EINVAL;
>
> - mem = mm_iommu_find(current->mm, vaddr, size >> PAGE_SHIFT);
> + mem = mm_iommu_find(container->mm, vaddr, size >> PAGE_SHIFT);
> if (!mem)
> return -ENOENT;
>
> - return mm_iommu_put(current->mm, mem);
> + return mm_iommu_put(container->mm, mem);
> }
>
> static long tce_iommu_register_pages(struct tce_container *container,
> @@ -128,14 +140,11 @@ static long tce_iommu_register_pages(struct tce_container *container,
> struct mm_iommu_table_group_mem_t *mem = NULL;
> unsigned long entries = size >> PAGE_SHIFT;
>
> - if (!current || !current->mm)
> - return -ESRCH; /* process exited */
> -
> if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK) ||
> ((vaddr + size) < vaddr))
> return -EINVAL;
>
> - ret = mm_iommu_get(current->mm, vaddr, entries, &mem);
> + ret = mm_iommu_get(container->mm, vaddr, entries, &mem);
> if (ret)
> return ret;
>
> @@ -144,7 +153,8 @@ static long tce_iommu_register_pages(struct tce_container *container,
> return 0;
> }
>
> -static long tce_iommu_userspace_view_alloc(struct iommu_table *tbl)
> +static long tce_iommu_userspace_view_alloc(struct iommu_table *tbl,
> + struct mm_struct *mm)
> {
> unsigned long cb = _ALIGN_UP(sizeof(tbl->it_userspace[0]) *
> tbl->it_size, PAGE_SIZE);
> @@ -153,13 +163,13 @@ static long tce_iommu_userspace_view_alloc(struct iommu_table *tbl)
>
> BUG_ON(tbl->it_userspace);
>
> - ret = try_increment_locked_vm(cb >> PAGE_SHIFT);
> + ret = try_increment_locked_vm(mm, cb >> PAGE_SHIFT);
> if (ret)
> return ret;
>
> uas = vzalloc(cb);
> if (!uas) {
> - decrement_locked_vm(cb >> PAGE_SHIFT);
> + decrement_locked_vm(mm, cb >> PAGE_SHIFT);
> return -ENOMEM;
> }
> tbl->it_userspace = uas;
> @@ -167,7 +177,8 @@ static long tce_iommu_userspace_view_alloc(struct iommu_table *tbl)
> return 0;
> }
>
> -static void tce_iommu_userspace_view_free(struct iommu_table *tbl)
> +static void tce_iommu_userspace_view_free(struct iommu_table *tbl,
> + struct mm_struct *mm)
> {
> unsigned long cb = _ALIGN_UP(sizeof(tbl->it_userspace[0]) *
> tbl->it_size, PAGE_SIZE);
> @@ -177,7 +188,7 @@ static void tce_iommu_userspace_view_free(struct iommu_table *tbl)
>
> vfree(tbl->it_userspace);
> tbl->it_userspace = NULL;
> - decrement_locked_vm(cb >> PAGE_SHIFT);
> + decrement_locked_vm(mm, cb >> PAGE_SHIFT);
> }
>
> static bool tce_page_is_contained(struct page *page, unsigned page_shift)
> @@ -237,9 +248,6 @@ static int tce_iommu_enable(struct tce_container *container)
> struct iommu_table_group *table_group;
> struct tce_iommu_group *tcegrp;
>
> - if (!current->mm)
> - return -ESRCH; /* process exited */
> -
> if (container->enabled)
> return -EBUSY;
>
> @@ -284,8 +292,12 @@ static int tce_iommu_enable(struct tce_container *container)
> if (!table_group->tce32_size)
> return -EPERM;
>
> + ret = tce_iommu_mm_set(container);
> + if (ret)
> + return ret;
> +
> locked = table_group->tce32_size >> PAGE_SHIFT;
> - ret = try_increment_locked_vm(locked);
> + ret = try_increment_locked_vm(container->mm, locked);
> if (ret)
> return ret;
>
> @@ -303,10 +315,8 @@ static void tce_iommu_disable(struct tce_container *container)
>
> container->enabled = false;
>
> - if (!current->mm)
> - return;
> -
> - decrement_locked_vm(container->locked_pages);
> + BUG_ON(!container->mm);
> + decrement_locked_vm(container->mm, container->locked_pages);
> }
>
> static void *tce_iommu_open(unsigned long arg)
> @@ -333,7 +343,8 @@ static void *tce_iommu_open(unsigned long arg)
> static int tce_iommu_clear(struct tce_container *container,
> struct iommu_table *tbl,
> unsigned long entry, unsigned long pages);
> -static void tce_iommu_free_table(struct iommu_table *tbl);
> +static void tce_iommu_free_table(struct tce_container *container,
> + struct iommu_table *tbl);
>
> static void tce_iommu_release(void *iommu_data)
> {
> @@ -358,10 +369,12 @@ static void tce_iommu_release(void *iommu_data)
> continue;
>
> tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> - tce_iommu_free_table(tbl);
> + tce_iommu_free_table(container, tbl);
> }
>
> tce_iommu_disable(container);
> + if (container->mm)
> + mmdrop(container->mm);
> mutex_destroy(&container->lock);
>
> kfree(container);
> @@ -376,13 +389,14 @@ static void tce_iommu_unuse_page(struct tce_container *container,
> put_page(page);
> }
>
> -static int tce_iommu_prereg_ua_to_hpa(unsigned long tce, unsigned long size,
> +static int tce_iommu_prereg_ua_to_hpa(struct tce_container *container,
> + unsigned long tce, unsigned long size,
> unsigned long *phpa, struct mm_iommu_table_group_mem_t **pmem)
> {
> long ret = 0;
> struct mm_iommu_table_group_mem_t *mem;
>
> - mem = mm_iommu_lookup(current->mm, tce, size);
> + mem = mm_iommu_lookup(container->mm, tce, size);
> if (!mem)
> return -EINVAL;
>
> @@ -395,18 +409,18 @@ static int tce_iommu_prereg_ua_to_hpa(unsigned long tce, unsigned long size,
> return 0;
> }
>
> -static void tce_iommu_unuse_page_v2(struct iommu_table *tbl,
> - unsigned long entry)
> +static void tce_iommu_unuse_page_v2(struct tce_container *container,
> + struct iommu_table *tbl, unsigned long entry)
> {
> struct mm_iommu_table_group_mem_t *mem = NULL;
> int ret;
> unsigned long hpa = 0;
> unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
>
> - if (!pua || !current || !current->mm)
> + if (!pua)
> return;
>
> - ret = tce_iommu_prereg_ua_to_hpa(*pua, IOMMU_PAGE_SIZE(tbl),
> + ret = tce_iommu_prereg_ua_to_hpa(container, *pua, IOMMU_PAGE_SIZE(tbl),
> &hpa, &mem);
> if (ret)
> pr_debug("%s: tce %lx at #%lx was not cached, ret=%d\n",
> @@ -436,7 +450,7 @@ static int tce_iommu_clear(struct tce_container *container,
> continue;
>
> if (container->v2) {
> - tce_iommu_unuse_page_v2(tbl, entry);
> + tce_iommu_unuse_page_v2(container, tbl, entry);
> continue;
> }
>
> @@ -517,7 +531,7 @@ static long tce_iommu_build_v2(struct tce_container *container,
> enum dma_data_direction dirtmp;
>
> if (!tbl->it_userspace) {
> - ret = tce_iommu_userspace_view_alloc(tbl);
> + ret = tce_iommu_userspace_view_alloc(tbl, container->mm);
> if (ret)
> return ret;
> }
> @@ -527,8 +541,8 @@ static long tce_iommu_build_v2(struct tce_container *container,
> unsigned long *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl,
> entry + i);
>
> - ret = tce_iommu_prereg_ua_to_hpa(tce, IOMMU_PAGE_SIZE(tbl),
> - &hpa, &mem);
> + ret = tce_iommu_prereg_ua_to_hpa(container,
> + tce, IOMMU_PAGE_SIZE(tbl), &hpa, &mem);
> if (ret)
> break;
>
> @@ -549,7 +563,7 @@ static long tce_iommu_build_v2(struct tce_container *container,
> ret = iommu_tce_xchg(tbl, entry + i, &hpa, &dirtmp);
> if (ret) {
> /* dirtmp cannot be DMA_NONE here */
> - tce_iommu_unuse_page_v2(tbl, entry + i);
> + tce_iommu_unuse_page_v2(container, tbl, entry + i);
> pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx, ret=%ld\n",
> __func__, entry << tbl->it_page_shift,
> tce, ret);
> @@ -557,7 +571,7 @@ static long tce_iommu_build_v2(struct tce_container *container,
> }
>
> if (dirtmp != DMA_NONE)
> - tce_iommu_unuse_page_v2(tbl, entry + i);
> + tce_iommu_unuse_page_v2(container, tbl, entry + i);
>
> *pua = tce;
>
> @@ -585,7 +599,7 @@ static long tce_iommu_create_table(struct tce_container *container,
> if (!table_size)
> return -EINVAL;
>
> - ret = try_increment_locked_vm(table_size >> PAGE_SHIFT);
> + ret = try_increment_locked_vm(container->mm, table_size >> PAGE_SHIFT);
> if (ret)
> return ret;
>
> @@ -598,13 +612,14 @@ static long tce_iommu_create_table(struct tce_container *container,
> return ret;
> }
>
> -static void tce_iommu_free_table(struct iommu_table *tbl)
> +static void tce_iommu_free_table(struct tce_container *container,
> + struct iommu_table *tbl)
> {
> unsigned long pages = tbl->it_allocated_size >> PAGE_SHIFT;
>
> - tce_iommu_userspace_view_free(tbl);
> + tce_iommu_userspace_view_free(tbl, container->mm);
> tbl->it_ops->free(tbl);
> - decrement_locked_vm(pages);
> + decrement_locked_vm(container->mm, pages);
> }
>
> static long tce_iommu_create_window(struct tce_container *container,
> @@ -667,7 +682,7 @@ static long tce_iommu_create_window(struct tce_container *container,
> table_group = iommu_group_get_iommudata(tcegrp->grp);
> table_group->ops->unset_window(table_group, num);
> }
> - tce_iommu_free_table(tbl);
> + tce_iommu_free_table(container, tbl);
>
> return ret;
> }
> @@ -705,7 +720,7 @@ static long tce_iommu_remove_window(struct tce_container *container,
>
> /* Free table */
> tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> - tce_iommu_free_table(tbl);
> + tce_iommu_free_table(container, tbl);
> container->tables[num] = NULL;
>
> return 0;
> @@ -760,7 +775,17 @@ static long tce_iommu_ioctl(void *iommu_data,
> }
>
> return (ret < 0) ? 0 : ret;
> + }
>
> + /*
> + * Sanity check to prevent one userspace from manipulating
> + * another userspace mm.
> + */
> + BUG_ON(!container);
> + if (container->mm && container->mm != current->mm)
> + return -EPERM;
> +
> + switch (cmd) {
> case VFIO_IOMMU_SPAPR_TCE_GET_INFO: {
> struct vfio_iommu_spapr_tce_info info;
> struct tce_iommu_group *tcegrp;
> @@ -929,6 +954,10 @@ static long tce_iommu_ioctl(void *iommu_data,
> minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
> size);
>
> + ret = tce_iommu_mm_set(container);
> + if (ret)
> + return ret;
> +
> if (copy_from_user(¶m, (void __user *)arg, minsz))
> return -EFAULT;
>
> @@ -952,6 +981,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> if (!container->v2)
> break;
>
> + if (!container->mm)
> + return -EPERM;
> +
> minsz = offsetofend(struct vfio_iommu_spapr_register_memory,
> size);
>
> @@ -1010,6 +1042,10 @@ static long tce_iommu_ioctl(void *iommu_data,
> if (!container->v2)
> break;
>
> + ret = tce_iommu_mm_set(container);
> + if (ret)
> + return ret;
> +
> if (!tce_groups_attached(container))
> return -ENXIO;
>
> @@ -1048,6 +1084,9 @@ static long tce_iommu_ioctl(void *iommu_data,
> if (!container->v2)
> break;
>
> + if (!container->mm)
> + return -EPERM;
> +
This is the VFIO_IOMMU_SPAPR_TCE_REMOVE path, isn't it? In which case
I think this is not quite right. IIUC it would be correct to create
the container, attach a group, then remove the default window before
creating new windows and starting mapping. That would cause an EPERM
here because we haven't set the mm yet.
So, I think this needs to be a tce_iommu_mm_set() instead.
> if (!tce_groups_attached(container))
> return -ENXIO;
>
> @@ -1093,7 +1132,7 @@ static void tce_iommu_release_ownership(struct tce_container *container,
> continue;
>
> tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> - tce_iommu_userspace_view_free(tbl);
> + tce_iommu_userspace_view_free(tbl, container->mm);
> if (tbl->it_map)
> iommu_release_ownership(tbl);
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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