[PATCH] tee: add overflow check in tee_ioctl_shm_register()

[Jens Wiklander <jens.wiklander@linaro.org>]

commit 573ae4f13f630d6660008f1974c0a8a29c30e18a upstream.

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

This may cause pin_user_pages_fast() to do a NULL pointer dereference.

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

Fixes: 033ddf12bcf5 ("tee: add register user memory")
Cc: stable@vger.kernel.org # 5.4
Reported-by: Nimish Mishra <neelam.nimish@gmail.com>
Reported-by: Anirban Chakraborty <ch.anirban00727@gmail.com>
Reported-by: Debdeep Mukhopadhyay <debdeep.mukhopadhyay@gmail.com>
Suggested-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[JW: backport to stable-5.4 + update commit message]
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
---
 drivers/tee/tee_core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tee/tee_core.c b/drivers/tee/tee_core.c
index a7ccd4d2bd10..2db144d2d26f 100644
--- a/drivers/tee/tee_core.c
+++ b/drivers/tee/tee_core.c
@@ -182,6 +182,9 @@ tee_ioctl_shm_register(struct tee_context *ctx,
 	if (data.flags)
 		return -EINVAL;
 
+	if (!access_ok((void __user *)(unsigned long)data.addr, data.length))
+		return -EFAULT;
+
 	shm = tee_shm_register(ctx, data.addr, data.length,
 			       TEE_SHM_DMA_BUF | TEE_SHM_USER_MAPPED);
 	if (IS_ERR(shm))
-- 
2.31.1