From: Ira Weiny ira.weiny@intel.com

The kernel pages used by shm_get_kernel_pages() are allocated using GFP_KERNEL through the following call stack:

trusted_instantiate() trusted_payload_alloc() -> GFP_KERNEL <trusted key op> tee_shm_register_kernel_buf() register_shm_helper() shm_get_kernel_pages()

Where <trusted key op> is one of:

trusted_key_unseal() trusted_key_get_random() trusted_key_seal()

Remove the vmalloc page support from shm_get_kernel_pages(). Replace with a warn on once.

Cc: Jens Wiklander jens.wiklander@linaro.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: "Fabio M. De Francesco" fmdefrancesco@gmail.com Cc: Christoph Hellwig hch@lst.de Cc: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ira Weiny ira.weiny@intel.com

--- Jens I went with the suggestion from Linus and Christoph and rejected vmalloc addresses. I did not hear back from you regarding Linus' question if the vmalloc page support was required by an up coming patch set or not. So I assumed it was something out of tree. --- drivers/tee/tee_shm.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index 27295bda3e0b..527a6eabc03e 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -24,37 +24,25 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count) static int shm_get_kernel_pages(unsigned long start, size_t page_count, struct page **pages) { + struct kvec *kiov; size_t n; int rc;

- if (is_vmalloc_addr((void *)start)) { - struct page *page; - - for (n = 0; n < page_count; n++) { - page = vmalloc_to_page((void *)(start + PAGE_SIZE * n)); - if (!page) - return -ENOMEM; - - get_page(page); - pages[n] = page; - } - rc = page_count; - } else { - struct kvec *kiov; - - kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL); - if (!kiov) - return -ENOMEM; + if (WARN_ON_ONCE(is_vmalloc_addr((void *)start))) + return -EINVAL;

- for (n = 0; n < page_count; n++) { - kiov[n].iov_base = (void *)(start + n * PAGE_SIZE); - kiov[n].iov_len = PAGE_SIZE; - } + kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL); + if (!kiov) + return -ENOMEM;

- rc = get_kernel_pages(kiov, page_count, 0, pages); - kfree(kiov); + for (n = 0; n < page_count; n++) { + kiov[n].iov_base = (void *)(start + n * PAGE_SIZE); + kiov[n].iov_len = PAGE_SIZE; }

+ rc = get_kernel_pages(kiov, page_count, 0, pages); + kfree(kiov); + return rc; }

From: Ira Weiny ira.weiny@intel.com

The only caller to get_kernel_pages() [shm_get_kernel_pages()] has been updated to not need it.

Remove get_kernel_pages().

Cc: Mel Gorman mgorman@suse.de Cc: Al Viro viro@zeniv.linux.org.uk Cc: "Fabio M. De Francesco" fmdefrancesco@gmail.com Cc: Christoph Hellwig hch@lst.de Cc: Andrew Morton akpm@linux-foundation.org Signed-off-by: Ira Weiny ira.weiny@intel.com --- include/linux/mm.h | 2 -- mm/swap.c | 30 ------------------------------ 2 files changed, 32 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h index 8bbcccbc5565..9a06df4f057c 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1969,8 +1969,6 @@ int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, struct task_struct *task, bool bypass_rlim);

struct kvec; -int get_kernel_pages(const struct kvec *iov, int nr_pages, int write, - struct page **pages); struct page *get_dump_page(unsigned long addr);

bool folio_mark_dirty(struct folio *folio); diff --git a/mm/swap.c b/mm/swap.c index 955930f41d20..a9aa648eb0d0 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -157,36 +157,6 @@ void put_pages_list(struct list_head *pages) } EXPORT_SYMBOL(put_pages_list);

-/* - * get_kernel_pages() - pin kernel pages in memory - * @kiov: An array of struct kvec structures - * @nr_segs: number of segments to pin - * @write: pinning for read/write, currently ignored - * @pages: array that receives pointers to the pages pinned. - * Should be at least nr_segs long. - * - * Returns number of pages pinned. This may be fewer than the number requested. - * If nr_segs is 0 or negative, returns 0. If no pages were pinned, returns 0. - * Each page returned must be released with a put_page() call when it is - * finished with. - */ -int get_kernel_pages(const struct kvec *kiov, int nr_segs, int write, - struct page **pages) -{ - int seg; - - for (seg = 0; seg < nr_segs; seg++) { - if (WARN_ON(kiov[seg].iov_len != PAGE_SIZE)) - return seg; - - pages[seg] = kmap_to_page(kiov[seg].iov_base); - get_page(pages[seg]); - } - - return seg; -} -EXPORT_SYMBOL_GPL(get_kernel_pages); - typedef void (*move_fn_t)(struct lruvec *lruvec, struct folio *folio);

static void lru_add_fn(struct lruvec *lruvec, struct folio *folio)

On Sun, Oct 02, 2022 at 01:46:41AM +0100, Al Viro wrote:

On Sat, Oct 01, 2022 at 05:23:25PM -0700, ira.weiny@intel.com wrote:

...

kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL); @@ -38,12 +39,12 @@ static int shm_get_kernel_pages(unsigned long start, size_t page_count, for (n = 0; n < page_count; n++) { kiov[n].iov_base = (void *)(start + n * PAGE_SIZE); kiov[n].iov_len = PAGE_SIZE;

• pages[n] = virt_to_page(kiov[n].iov_base);
  

• get_page(pages[n]);
  

  }

• rc = get_kernel_pages(kiov, page_count, 0, pages); kfree(kiov);

IDGI. The only thing in kiov[...] you are every reading is ->iov_base. And you fetch it once, right after the assignment.

:-( Good point. Thanks for catching that. I was too focused on just replacing get_kernel_pages() with get_page() and I should have refactored more.

Why bother with allocating the array at all? pages[n] = virt_to_page((void *)start + n * PAGE_SIZE); would do just as well, not to mention the fact that since you reject vmalloc and kmap, you might simply do

page = virt_to_page(start); for (int n = 0; n < page_count; n++) get_page(pages[n] = page + n);

I think I'd avoid the assignment in the parameter as I would miss that if I came back and looked at this code later.

I'll get rid of the kiov in v2.

Sorry for not cleaning it up more and thanks for the review!

Ira

+ Phil

Hi Ira,

On Sun, 2 Oct 2022 at 05:53, ira.weiny@intel.com wrote:

From: Ira Weiny ira.weiny@intel.com

The kernel pages used by shm_get_kernel_pages() are allocated using GFP_KERNEL through the following call stack:

trusted_instantiate() trusted_payload_alloc() -> GFP_KERNEL <trusted key op> tee_shm_register_kernel_buf() register_shm_helper() shm_get_kernel_pages()

Where <trusted key op> is one of:

    trusted_key_unseal()
    trusted_key_get_random()
    trusted_key_seal()

Remove the vmalloc page support from shm_get_kernel_pages(). Replace with a warn on once.

Cc: Jens Wiklander jens.wiklander@linaro.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: "Fabio M. De Francesco" fmdefrancesco@gmail.com Cc: Christoph Hellwig hch@lst.de Cc: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Ira Weiny ira.weiny@intel.com

---

Jens I went with the suggestion from Linus and Christoph and rejected vmalloc addresses. I did not hear back from you regarding Linus' question if the vmalloc page support was required by an up coming patch set or not. So I assumed it was something out of tree.

It looks like I wasn't CC'd to that conversation. IIRC, support for vmalloc addresses was added recently by Phil here [1]. So I would like to give him a chance if he is planning to post a corresponding kernel driver upstream.

[1] https://lists.trustedfirmware.org/archives/list/op-tee@lists.trustedfirmware...

-Sumit

---

drivers/tee/tee_shm.c | 36 ++++++++++++------------------------ 1 file changed, 12 insertions(+), 24 deletions(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index 27295bda3e0b..527a6eabc03e 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -24,37 +24,25 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count) static int shm_get_kernel_pages(unsigned long start, size_t page_count, struct page **pages) {

•   struct kvec *kiov;
    size_t n;
    int rc;
  
  

•   if (is_vmalloc_addr((void *)start)) {
  

•           struct page *page;
  

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

•                   page = vmalloc_to_page((void *)(start + PAGE_SIZE * n));
  

•                   if (!page)
  

•                           return -ENOMEM;
  

•                   get_page(page);
  

•                   pages[n] = page;
  

•           }
  

•           rc = page_count;
  

•   } else {
  

•           struct kvec *kiov;
  

•           kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL);
  

•           if (!kiov)
  

•                   return -ENOMEM;
  

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

•           return -EINVAL;
  
  

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

•                   kiov[n].iov_base = (void *)(start + n * PAGE_SIZE);
  

•                   kiov[n].iov_len = PAGE_SIZE;
  

•           }
  

•   kiov = kcalloc(page_count, sizeof(*kiov), GFP_KERNEL);
  

•   if (!kiov)
  

•           return -ENOMEM;
  
  

•           rc = get_kernel_pages(kiov, page_count, 0, pages);
  

•           kfree(kiov);
  

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

•           kiov[n].iov_base = (void *)(start + n * PAGE_SIZE);
  

•           kiov[n].iov_len = PAGE_SIZE;
    }
  
  

•   rc = get_kernel_pages(kiov, page_count, 0, pages);
  

•   kfree(kiov);
  

•   return rc;
  

}

-- 2.37.2