Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration

On 11/30/23 08:54, Sumit Garg wrote:

On Wed, 29 Nov 2023 at 22:15, Arnaud Pouliquen arnaud.pouliquen@foss.st.com wrote:

...

Currently it's not possible to register kernel buffers with TEE which are allocated via vmalloc.

Use iov_iter and associated helper functions to manage the page registration for all type of memories.

Suggested-by: Christoph Hellwig hch@infradead.org Signed-off-by: Arnaud Pouliquen arnaud.pouliquen@foss.st.com

---

Update from V3 to V4:

• improve commit message,
• use import_ubuf() instead of iov_iter_init(),
• move shm_get_kernel_pages in register_shm_helper,
• put back untagged_addr in register_shm_helper(),
• move the comment related to pin pages from shm_get_kernel_pages() to register_shm_helper().

Update from V2 to V3:

• break lines longer than 80 columns.

Update from V1 to V2:

• replace ITER_SOURCE by ITER_DEST flag in tee_shm_register_user_buf(),
• replace IS_ERR_OR NULL(shm) by IS_ERR(shm) in tee_shm_register_user_buf().

V1: The support of buffer registration allocated with vmalloc is no more available since c83900393aa1 ("tee: Remove vmalloc page support").

This patch is an alternative to a revert and resulted from a discussion with Christopher Hellwig [1].

This patch has been tested using xtest tool in optee qemu environment [2] and using the series related to the remoteproc tee that should be proposed soon [3].

References: [1] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb... [2] https://optee.readthedocs.io/en/latest/building/devices/qemu.html#build-inst... [3] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb...

---

drivers/tee/tee_shm.c | 83 ++++++++++++++++++++++++------------------- 1 file changed, 46 insertions(+), 37 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index 673cf0359494..ac73e8143233 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -22,23 +22,12 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count) put_page(pages[n]); }

-static int shm_get_kernel_pages(unsigned long start, size_t page_count,

•                           struct page **pages)
  

+static void shm_get_kernel_pages(struct page **pages, size_t page_count) {

•   struct page *page;
    size_t n;
  
  

•   if (WARN_ON_ONCE(is_vmalloc_addr((void *)start) ||
  

•                    is_kmap_addr((void *)start)))
  

•           return -EINVAL;
  

•   page = virt_to_page((void *)start);
  

•   for (n = 0; n < page_count; n++) {
  

•           pages[n] = page + n;
  

•   for (n = 0; n < page_count; n++)
            get_page(pages[n]);
  

•   }
  

•   return page_count;
  

}

static void release_registered_pages(struct tee_shm *shm) @@ -214,13 +203,14 @@ struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size) EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);

static struct tee_shm * -register_shm_helper(struct tee_context *ctx, unsigned long addr,

•               size_t length, u32 flags, int id)
  

+register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,

•               int id)
  

{ struct tee_device *teedev = ctx->teedev; struct tee_shm *shm;

•   unsigned long start;
  

•   size_t num_pages;
  

•   unsigned long start, addr;
  

•   size_t num_pages, off;
  

•   ssize_t len;
    void *ret;
    int rc;
  
  

@@ -245,31 +235,38 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr, shm->flags = flags; shm->ctx = ctx; shm->id = id;

•   addr = untagged_addr(addr);
  

•   addr = untagged_addr((unsigned long)iter_iov_addr(iter));
    start = rounddown(addr, PAGE_SIZE);
  

•   shm->offset = addr - start;
  

•   shm->size = length;
  

•   num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
  

•   num_pages = iov_iter_npages(iter, INT_MAX);
  

•   if (!num_pages) {
  

•           ret = ERR_PTR(-ENOMEM);
  

•           goto err_ctx_put;
  

•   }
  

•   shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
    if (!shm->pages) {
            ret = ERR_PTR(-ENOMEM);
            goto err_free_shm;
    }
  
  

•   if (flags & TEE_SHM_USER_MAPPED)
  

•           rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
  

•                                    shm->pages);
  

•   else
  

•           rc = shm_get_kernel_pages(start, num_pages, shm->pages);
  

•   if (rc > 0)
  

•           shm->num_pages = rc;
  

•   if (rc != num_pages) {
  

•           if (rc >= 0)
  

•                   rc = -ENOMEM;
  

•           ret = ERR_PTR(rc);
  

•           goto err_put_shm_pages;
  

•   len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
  

•                                &off);
  

•   if (unlikely(len <= 0)) {
  

•           ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM);
  

•           goto err_free_shm_pages;
    }
  
  

•   /*
  

•    * iov_iter_extract_kvec_pages does not get reference on the pages,
  

•    * get a pin on them.
  

I think you meant: "get a reference on them". But I don't see the value of this comment since iov_iter_extract_kvec_pages() already has been commented properly as follows:

/*

• Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
• This does not get references on the pages, nor does it get a pin on them.

*/

I spent some time debugging this part. Since we use the same API for both user and kernel buffers, we wouldn't expect to have any specific actions to take. Therefore, I thought it would be helpful to add a comment explaining the reason for this specific code, rather than go deeper into iov_iter to understand it.

But if you don't see the value, I can remove the comment.

...

•    */
  

•   if (iov_iter_is_kvec(iter))
  

•           shm_get_kernel_pages(shm->pages, num_pages);
  

•   shm->offset = off;
  

•   shm->size = len;
  

•   shm->num_pages = num_pages;
  

•   rc = teedev->desc->ops->shm_register(ctx, shm, shm->pages,
                                         shm->num_pages, start);
    if (rc) {
  

@@ -279,10 +276,11 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,

    return shm;

err_put_shm_pages:

•   if (flags & TEE_SHM_USER_MAPPED)
  

•   if (!iov_iter_is_kvec(iter))
            unpin_user_pages(shm->pages, shm->num_pages);
    else
            shm_put_kernel_pages(shm->pages, shm->num_pages);
  

+err_free_shm_pages: kfree(shm->pages); err_free_shm: kfree(shm); @@ -307,8 +305,9 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx, u32 flags = TEE_SHM_USER_MAPPED | TEE_SHM_DYNAMIC; struct tee_device *teedev = ctx->teedev; struct tee_shm *shm;

•   struct iov_iter iter;
    void *ret;
  

•   int id;
  

•   int id, err;
  
    if (!access_ok((void __user *)addr, length))
            return ERR_PTR(-EFAULT);
  

@@ -319,7 +318,11 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx, if (id < 0) return ERR_PTR(id);

•   shm = register_shm_helper(ctx, addr, length, flags, id);
  

•   err = import_ubuf(ITER_DEST, (void __user *)addr, length, &iter);
  

As I mentioned in a previous review, import_ubuf() already does the access_ok() check, so we don't need the extra access_ok() check above. Also, you should move import_ubuf() to be the first invocation within this API.

My apologies, I re-added import_ubuf() during testing to debug an issue and forgot to remove it afterwards.

Thanks and regards, Arnaud

-Sumit

...

•   if (err)
  

•           return ERR_PTR(err);
  

•   shm = register_shm_helper(ctx, &iter, flags, id);
    if (IS_ERR(shm)) {
            mutex_lock(&teedev->mutex);
            idr_remove(&teedev->idr, id);
  

@@ -352,8 +355,14 @@ struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx, void *addr, size_t length) { u32 flags = TEE_SHM_DYNAMIC;

•   struct kvec kvec;
  

•   struct iov_iter iter;
  

•   kvec.iov_base = addr;
  

•   kvec.iov_len = length;
  

•   iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, length);
  
  

•   return register_shm_helper(ctx, (unsigned long)addr, length, flags, -1);
  

•   return register_shm_helper(ctx, &iter, flags, -1);
  

} EXPORT_SYMBOL_GPL(tee_shm_register_kernel_buf);

-- 2.25.1