Re: [PATCH -next V2 1/2] sata_fsl: fix UAF in sata_fsl_port_stop when rmmod sata_fsl

[Sergei Shtylyov <sergei.shtylyov@gmail.com>]

Hello!

On 20.11.2021 6:34, Baokun Li wrote:

> When the `rmmod sata_fsl.ko` command is executed in the PPC64 GNU/Linux,
> a bug is reported:
>   ==================================================================
>   BUG: Unable to handle kernel data access on read at 0x80000800805b502c
>   Oops: Kernel access of bad area, sig: 11 [#1]
>   NIP [c0000000000388a4] .ioread32+0x4/0x20
>   LR [80000000000c6034] .sata_fsl_port_stop+0x44/0xe0 [sata_fsl]
>   Call Trace:
>    .free_irq+0x1c/0x4e0 (unreliable)
>    .ata_host_stop+0x74/0xd0 [libata]
>    .release_nodes+0x330/0x3f0
>    .device_release_driver_internal+0x178/0x2c0
>    .driver_detach+0x64/0xd0
>    .bus_remove_driver+0x70/0xf0
>    .driver_unregister+0x38/0x80
>    .platform_driver_unregister+0x14/0x30
>    .fsl_sata_driver_exit+0x18/0xa20 [sata_fsl]
>    .__se_sys_delete_module+0x1ec/0x2d0
>    .system_call_exception+0xfc/0x1f0
>    system_call_common+0xf8/0x200
>   ==================================================================
> 
> The triggering of the BUG is shown in the following stack:
> 
> driver_detach
>    device_release_driver_internal
>      __device_release_driver
>        drv->remove(dev) --> platform_drv_remove/platform_remove
>          drv->remove(dev) --> sata_fsl_remove
>            iounmap(host_priv->hcr_base);			<---- unmap
>            kfree(host_priv);                             <---- free
>        devres_release_all
>          release_nodes
>            dr->node.release(dev, dr->data) --> ata_host_stop
>              ap->ops->port_stop(ap) --> sata_fsl_port_stop
>                  ioread32(hcr_base + HCONTROL)           <---- UAF
>              host->ops->host_stop(host)
> 
> The iounmap(host_priv->hcr_base) and kfree(host_priv) commands should

    s/commands/functions/?

> not be executed in drv->remove. These commands should be executed in
> host_stop after port_stop. Therefore, we move these commands to the
> new function sata_fsl_host_stop and bind the new function to host_stop
> by referring to achi.

    You mean AHCI? I don't see where you reference ahci (or achi)...

> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>

    Doesn't this need to go into the stable trees?

> ---
>   drivers/ata/sata_fsl.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/sata_fsl.c b/drivers/ata/sata_fsl.c
> index e5838b23c9e0..30759fd1c3a2 100644
> --- a/drivers/ata/sata_fsl.c
> +++ b/drivers/ata/sata_fsl.c
> @@ -1430,12 +1430,25 @@ static struct ata_port_operations sata_fsl_ops = {
>   	.pmp_detach = sata_fsl_pmp_detach,
>   };
>   
> +static void sata_fsl_host_stop(struct ata_host *host)
> +{
> +	struct sata_fsl_host_priv *host_priv = host->private_data;
> +
> +	iounmap(host_priv->hcr_base);
> +	kfree(host_priv);
> +}
> +
> +static struct ata_port_operations sata_fsl_platform_ops = {
> +	.inherits       = &sata_fsl_ops,
> +	.host_stop      = sata_fsl_host_stop,

    Why not just add it to the initializer for sata_fsl_ops?

[...]

MBR, Sergei