Re: [ndctl PATCH] ndctl: Work around kernel memory corruption

[Dave Jiang <dave.jiang@intel.com>]

On 08/13/2018 01:31 PM, Keith Busch wrote:
> Kernel commit efda1b5d87cb ("acpi, nfit, libnvdimm: fix / harden
> ars_status output length handling") contained an incorrect ars status
> output size calculation and may overrun the buffer provided by 4
> bytes. This patch adds 4 bytes to the buffer the user space allocates
> so that the kernel's overrun doesn't corrupt the application's heap.
> 
> See kernel patch for more details:
> 
>   https://patchwork.kernel.org/patch/10563103/
> 
> Signed-off-by: Keith Busch <keith.busch@intel.com>

Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> ---
>  ndctl/lib/ars.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/ndctl/lib/ars.c b/ndctl/lib/ars.c
> index c78e3bf..bd75131 100644
> --- a/ndctl/lib/ars.c
> +++ b/ndctl/lib/ars.c
> @@ -133,7 +133,16 @@ NDCTL_EXPORT struct ndctl_cmd *ndctl_bus_cmd_new_ars_status(struct ndctl_cmd *ar
>  	}
>  
>  	size = sizeof(*cmd) + ars_cap_cmd->max_ars_out;
> -	cmd = calloc(1, size);
> +
> +	/*
> +	 * Older kernels have a bug that miscalculates the output length of the
> +	 * ars status and will overrun the provided buffer by 4 bytes,
> +	 * corrupting the memory. Add an additional 4 bytes in the allocation
> +	 * size to prevent that corruption. See kernel patch for more details:
> +	 *
> +	 *   https://patchwork.kernel.org/patch/10563103/
> +	 */
> +	cmd = calloc(1, size + 4);
>  	if (!cmd)
>  		return NULL;
>  
> 
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