[PATCH 5.18 1/6] tee: add overflow check in register_shm_helper()

[Greg Kroah-Hartman]

From: Jens Wiklander <jens.wiklander@xxxxxxxxxx>

commit 573ae4f13f630d6660008f1974c0a8a29c30e18a upstream.

With special lengths supplied by user space, register_shm_helper() has
an integer overflow when calculating the number of pages covered by a
supplied user space memory region.

This causes internal_get_user_pages_fast() a helper function of
pin_user_pages_fast() to do a NULL pointer dereference:

  Unable to handle kernel NULL pointer dereference at virtual address 0000000000000010
  Modules linked in:
  CPU: 1 PID: 173 Comm: optee_example_a Not tainted 5.19.0 #11
  Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
  pc : internal_get_user_pages_fast+0x474/0xa80
  Call trace:
   internal_get_user_pages_fast+0x474/0xa80
   pin_user_pages_fast+0x24/0x4c
   register_shm_helper+0x194/0x330
   tee_shm_register_user_buf+0x78/0x120
   tee_ioctl+0xd0/0x11a0
   __arm64_sys_ioctl+0xa8/0xec
   invoke_syscall+0x48/0x114

Fix this by adding an an explicit call to access_ok() in
tee_shm_register_user_buf() to catch an invalid user space address
early.

Fixes: 033ddf12bcf5 ("tee: add register user memory")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Nimish Mishra <neelam.nimish@xxxxxxxxx>
Reported-by: Anirban Chakraborty <ch.anirban00727@xxxxxxxxx>
Reported-by: Debdeep Mukhopadhyay <debdeep.mukhopadhyay@xxxxxxxxx>
Suggested-by: Jerome Forissier <jerome.forissier@xxxxxxxxxx>
Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/tee/tee_shm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -311,6 +311,9 @@ struct tee_shm *tee_shm_register_user_bu
 	void *ret;
 	int id;
 
+	if (!access_ok((void __user *)addr, length))
+		return ERR_PTR(-EFAULT);
+
 	mutex_lock(&teedev->mutex);
 	id = idr_alloc(&teedev->idr, NULL, 1, 0, GFP_KERNEL);
 	mutex_unlock(&teedev->mutex);