On Tue, 3 Sep 2013, Matthew Garrett wrote:
> Allowing users to write to address space makes it possible for the kernel
> to be subverted, avoiding module loading restrictions. Prevent this when
> any restrictions have been imposed on loading modules.
>
> Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
Reviewed-by: James Morris <jmorris@xxxxxxxxx>
> ---
> drivers/char/mem.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/char/mem.c b/drivers/char/mem.c
> index 1af8664..61406c8 100644
> --- a/drivers/char/mem.c
> +++ b/drivers/char/mem.c
> @@ -159,6 +159,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf,
> unsigned long copied;
> void *ptr;
>
> + if (secure_modules())
> + return -EPERM;
> +
> if (!valid_phys_addr_range(p, count))
> return -EFAULT;
>
> @@ -497,6 +500,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf,
> char *kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */
> int err = 0;
>
> + if (secure_modules())
> + return -EPERM;
> +
> if (p < (unsigned long) high_memory) {
> unsigned long to_write = min_t(unsigned long, count,
> (unsigned long)high_memory - p);
> --
> 1.8.3.1
>
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--
James Morris
<jmorris@xxxxxxxxx>
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