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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Nimish Mishra <neelam.nimish@gmail.com>,
        Anirban Chakraborty <ch.anirban00727@gmail.com>,
        Debdeep Mukhopadhyay <debdeep.mukhopadhyay@gmail.com>,
        Jerome Forissier <jerome.forissier@linaro.org>,
        Jens Wiklander <jens.wiklander@linaro.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 5.10 540/545] tee: add overflow check in register_shm_helper()
Date:   Fri, 19 Aug 2022 17:45:10 +0200
Message-Id: <20220819153853.762825860@linuxfoundation.org>
In-Reply-To: <20220819153829.135562864@linuxfoundation.org>
References: <20220819153829.135562864@linuxfoundation.org>
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From: Jens Wiklander <jens.wiklander@linaro.org>

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@vger.kernel.org
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: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/tee/tee_shm.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -222,6 +222,9 @@ struct tee_shm *tee_shm_register(struct
 		goto err;
 	}
 
+	if (!access_ok((void __user *)addr, length))
+		return ERR_PTR(-EFAULT);
+
 	mutex_lock(&teedev->mutex);
 	shm->id = idr_alloc(&teedev->idr, shm, 1, 0, GFP_KERNEL);
 	mutex_unlock(&teedev->mutex);