Re: [PATCH 07/13] kexec: Implementation of new syscall kexec_file_load

WANG Chao
2014-06-06T06:56:47Z

On 06/03/14 at 09:06am, Vivek Goyal wrote:
> Previous patch provided the interface definition and this patch prvides
> implementation of new syscall.
>
> Previously segment list was prepared in user space. Now user space just
> passes kernel fd, initrd fd and command line and kernel will create a
> segment list internally.
>
> This patch contains generic part of the code. Actual segment preparation
> and loading is done by arch and image specific loader. Which comes in
> next patch.
>
> Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

[..]
> diff --git a/kernel/kexec.c b/kernel/kexec.c
> index a3044e6..1ad4d60 100644
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c

> +static int kimage_file_prepare_segments(struct kimage *image, int kernel_fd,
> + int initrd_fd, const char __user *cmdline_ptr,
> + unsigned long cmdline_len)
> +{
> + int ret = 0;
> + void *ldata;
> +
> + ret = copy_file_from_fd(kernel_fd, &image->kernel_buf,
> + &image->kernel_buf_len);
> + if (ret)
> + return ret;
> +
> + /* Call arch image probe handlers */
> + ret = arch_kexec_kernel_image_probe(image, image->kernel_buf,
> + image->kernel_buf_len);
> +
> + if (ret)
> + goto out;
> +
> + ret = copy_file_from_fd(initrd_fd, &image->initrd_buf,
> + &image->initrd_buf_len);
> + if (ret)
> + goto out;
> +
> + image->cmdline_buf = vzalloc(cmdline_len);

You should validate the upper/lower boundary of cmdline_len before
calling vzalloc. When cmdline_len is 0 or too large, vmalloc failure
message would be fired.

> + if (!image->cmdline_buf)
> + goto out;
> +
> + ret = copy_from_user(image->cmdline_buf, cmdline_ptr, cmdline_len);
> + if (ret) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + image->cmdline_buf_len = cmdline_len;
> +
> + /* command line should be a string with last byte null */
> + if (image->cmdline_buf[cmdline_len - 1] != '\0') {
> + ret = -EINVAL;
> + goto out;
> + }

Given the fact that command line is optional as well as initrd, I think
above chunk of code needs to update a bit for the case cmdline_len is 0
or cmdline_buf is pointing NULL?

Thanks
WANG Chao