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SubjectRe: [PATCH v2] tty: rocket: Fix a kernel address leak in rp_ioctl
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On 3/31/2019 11:02 AM, Fuqian Huang wrote:
> If the cmd is RCPK_GET_STRUCT, copy_to_user will copy
> info to user space. As info->port.ops is the address of
> a constant object rocket_port_ops (assigned in init_r_port),
> a kernel address leakage happens.
>
> This patch sets all the pointer fields to NULL before copy the
> object to user space to avoid kernel address leakage.


Should not this be done like provide userspace the stuff they want?

>
> Signed-off-by: Fuqian Huang <huangfq.daxian@gmail.com>
> ---
> drivers/tty/rocket.c | 31 +++++++++++++++++++++++++++++--
> 1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/rocket.c b/drivers/tty/rocket.c
> index b121d8f8f3d7..a7bcf44b61bd 100644
> --- a/drivers/tty/rocket.c
> +++ b/drivers/tty/rocket.c
> @@ -1271,6 +1271,34 @@ static int get_version(struct r_port *info, struct rocket_version __user *retver
> return 0;
> }
>
> +static int get_struct(struct r_port *info, void *argp)
Should not this void * argp be struct r_port __user ?
> +{
> + struct r_port *new;
> + int ret = 0;
> +
> + new = kzalloc(sizeof (struct r_port), GFP_KERNEL)

why there is space before sizeof everywhere ?

> ;
> + if (!new)
> + return -ENOMEM;
> + memcpy(new, info, sizeof (struct r_port));
> + new->port.tty = NULL;
> + new->port.itty = NULL;
> + new->port.ops = NULL;
> + new->port.client_ops = NULL;
> + memset(&new->port.open_wait.head, 0, sizeof (struct list_head));
> + memset(&new->port.delta_msr_wait.head, 0, sizeof (struct list_head));
> + memset(&new->port.mutex.wait_list, 0, sizeof (struct list_head));
> + memset(&new->port.buf_mutex.wait_list, 0, sizeof (struct list_head));
> + new->port.xmit_buf = NULL;
> + new->port.client_data = NULL;
> + new->ctlp = NULL;
> + new->xmit_buf = NULL;
> + memset(&new->write_mtx.wait_list, 0, sizeof (struct list_head));

Are we sure nothing is missed ?

Are the other information use by userspace ?


> + if (copy_to_user(argp, new, sizeof (struct r_port)))
> + ret = -EFAULT;
> + kfree(new);
> + return ret;
> +}
> +
> /* IOCTL call handler into the driver */
> static int rp_ioctl(struct tty_struct *tty,
> unsigned int cmd, unsigned long arg)
> @@ -1284,8 +1312,7 @@ static int rp_ioctl(struct tty_struct *tty,
>
> switch (cmd) {
> case RCKP_GET_STRUCT:
> - if (copy_to_user(argp, info, sizeof (struct r_port)))
> - ret = -EFAULT;
> + ret = get_struct(info, argp);
> break;
> case RCKP_GET_CONFIG:
> ret = get_config(info, argp);

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