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    Subject[PATCH 5.10 540/545] tee: add overflow check in register_shm_helper()
    Date
    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);

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