On Wed, Apr 30, 2025 at 2:12 PM Rouven Czerwinski rouven.czerwinski@linaro.org wrote:

Hi,

On Wed, 30 Apr 2025 at 13:53, Jens Wiklander jens.wiklander@linaro.org wrote:

...

On Mon, Apr 28, 2025 at 3:06 PM Jann Horn jannh@google.com wrote:

...

The current code around TEE_IOCTL_PARAM_SIZE() is a bit wrong on 32-bit kernels: Multiplying a user-provided 32-bit value with the size of a structure can wrap around on such platforms.

Fix it by using saturating arithmetic for the size calculation.

This has no security consequences because, in all users of TEE_IOCTL_PARAM_SIZE(), the subsequent kcalloc() implicitly checks for wrapping.

Signed-off-by: Jann Horn jannh@google.com

Note that I don't have a test device with a TEE; I only compile-tested the change on an x86-64 build.

---

drivers/tee/tee_core.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)

Looks good, I'm picking up this.

Thanks, Jens

...

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c index d113679b1e2d..acc7998758ad 100644 --- a/drivers/tee/tee_core.c +++ b/drivers/tee/tee_core.c @@ -10,6 +10,7 @@ #include <linux/fs.h> #include <linux/idr.h> #include <linux/module.h> +#include <linux/overflow.h> #include <linux/slab.h> #include <linux/tee_core.h> #include <linux/uaccess.h> @@ -19,7 +20,7 @@

#define TEE_NUM_DEVICES 32

-#define TEE_IOCTL_PARAM_SIZE(x) (sizeof(struct tee_param) * (x)) +#define TEE_IOCTL_PARAM_SIZE(x) (size_mul(sizeof(struct tee_param), (x)))

#define TEE_UUID_NS_NAME_SIZE 128

@@ -487,7 +488,7 @@ static int tee_ioctl_open_session(struct tee_context *ctx, if (copy_from_user(&arg, uarg, sizeof(arg))) return -EFAULT;

•   if (sizeof(arg) + TEE_IOCTL_PARAM_SIZE(arg.num_params) != buf.buf_len)
  

•   if (size_add(sizeof(arg), TEE_IOCTL_PARAM_SIZE(arg.num_params)) != buf.buf_len)
            return -EINVAL;
  
    if (arg.num_params) {
  

@@ -565,7 +566,7 @@ static int tee_ioctl_invoke(struct tee_context *ctx, if (copy_from_user(&arg, uarg, sizeof(arg))) return -EFAULT;

•   if (sizeof(arg) + TEE_IOCTL_PARAM_SIZE(arg.num_params) != buf.buf_len)
  

•   if (size_add(sizeof(arg), TEE_IOCTL_PARAM_SIZE(arg.num_params)) != buf.buf_len)
            return -EINVAL;
  
    if (arg.num_params) {
  

@@ -699,7 +700,7 @@ static int tee_ioctl_supp_recv(struct tee_context *ctx, if (get_user(num_params, &uarg->num_params)) return -EFAULT;

•   if (sizeof(*uarg) + TEE_IOCTL_PARAM_SIZE(num_params) != buf.buf_len)
  

•   if (size_add(sizeof(*uarg), TEE_IOCTL_PARAM_SIZE(num_params)) != buf.buf_len)
            return -EINVAL;
  
    params = kcalloc(num_params, sizeof(struct tee_param), GFP_KERNEL);
  

@@ -798,7 +799,7 @@ static int tee_ioctl_supp_send(struct tee_context *ctx, get_user(num_params, &uarg->num_params)) return -EFAULT;

•   if (sizeof(*uarg) + TEE_IOCTL_PARAM_SIZE(num_params) > buf.buf_len)
  

•   if (size_add(sizeof(*uarg), TEE_IOCTL_PARAM_SIZE(num_params)) > buf.buf_len)
            return -EINVAL;
  
    params = kcalloc(num_params, sizeof(struct tee_param), GFP_KERNEL);
  
  

---

base-commit: b4432656b36e5cc1d50a1f2dc15357543add530e change-id: 20250428-tee-sizecheck-299d5eff8fc7

-- Jann Horn jannh@google.com

I ran this through the arm32 qemu virt machine to test my new development setup, so:

Tested-by: Rouven Czerwinski rouven.czerwinski@linaro.org

Thanks for testing.

Cheers, Jens

Best regards, Rouven