On Mon, Sep 22, 2025 at 6:11 AM Sumit Garg sumit.garg@kernel.org wrote:

On Fri, Sep 19, 2025 at 02:40:16PM +0200, Jens Wiklander wrote:

...

In register_shm_helper(), fix incorrect error handling for a call to iov_iter_extract_pages(). A case is missing for when iov_iter_extract_pages() only got some pages and return a number larger than 0, but not the requested amount.

This fixes a possible NULL pointer dereference following a bad input from ioctl(TEE_IOC_SHM_REGISTER) where parts of the buffer isn't mapped.

Cc: stable@vger.kernel.org Reported-by: Masami Ichikawa masami256@gmail.com Closes: https://lore.kernel.org/op-tee/CACOXgS-Bo2W72Nj1_44c7bntyNYOavnTjJAvUbEiQfq=... Fixes: 7bdee4157591 ("tee: Use iov_iter to better support shared buffer registration") Signed-off-by: Jens Wiklander jens.wiklander@linaro.org

---

drivers/tee/tee_shm.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index daf6e5cfd59a..6ed7d030f4ed 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -316,7 +316,16 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,

  len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
                               &off);

• if (unlikely(len <= 0)) {
  

• if (DIV_ROUND_UP(len + off, PAGE_SIZE) != num_pages) {
  

•         if (len > 0) {
  

•                 /*
  

•                  * If we only got a few pages, update to release
  

•                  * the correct amount below.
  

•                  */
  

•                 shm->num_pages = len / PAGE_SIZE;
  

•                 ret = ERR_PTR(-ENOMEM);
  

•                 goto err_put_shm_pages;
  

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

Rather than operating directly on "len" without checking for error code first doesn't seems appropriate to me. How about following diff instead?

Sure, works for me.

diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c index daf6e5cfd59a..cb52bc51943e 100644 --- a/drivers/tee/tee_shm.c +++ b/drivers/tee/tee_shm.c @@ -319,6 +319,14 @@ register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags, if (unlikely(len <= 0)) { ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM); goto err_free_shm_pages;

•   } else if (DIV_ROUND_UP(len + off, PAGE_SIZE) != num_pages) {
  

•           /*
  

•            * If we only got a few pages, update to release the correct
  

•            * amount below.
  

•            */
  

•           shm->num_pages = len / PAGE_SIZE;
  

•           ret = ERR_PTR(-ENOMEM);
  

•           goto err_put_shm_pages;
    }
  
    /*
  

Thanks, Jens

-Sumit

...

-- 2.43.0