Re: [PATCH] x86/sgx: Add overflow check in sgx_validate_offset_length()

[Jarkko Sakkinen]

On Wed, Oct 05, 2022 at 12:59:03AM +0200, Borys wrote:
> sgx_validate_offset_length() function verifies "offset" and "length"
> arguments provided by userspace, but was missing an overflow check on
> their addition.
> This code was originally introduced in commit c6d26d370767 ("x86/sgx:
> Add SGX_IOC_ENCLAVE_ADD_PAGES") and later refactored in commit
> dda03e2c331b ("x86/sgx: Create utility to validate user provided offset
> and length").
> 
> Fixes: c6d26d370767 ("x86/sgx: Add SGX_IOC_ENCLAVE_ADD_PAGES")
> Signed-off-by: Borys Popławski <borysp@xxxxxxxxxxxxxxxxxxxxxx>
> ---
>  Applies on top of tip/x86/sgx ee56a283988d739c25d2d00ffb22707cb487ab47
> 
>  arch/x86/kernel/cpu/sgx/ioctl.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index ebe79d60619f..da8b8ea6b063 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -356,6 +356,9 @@ static int sgx_validate_offset_length(struct sgx_encl *encl,
>  	if (!length || !IS_ALIGNED(length, PAGE_SIZE))
>  		return -EINVAL;
>  
> +	if (offset + length < offset)
> +		return -EINVAL;
> +
>  	if (offset + length - PAGE_SIZE >= encl->size)
>  		return -EINVAL;
>  
> -- 
> 2.37.3
> 

Thank you.

Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx>

BTW, needs:

Cc: stable@xxxxxxxxxxxxxxx # v5.11+

BR, Jarkko