On 10/20, Tycho Andersen wrote:
>
> +long seccomp_get_filter(struct task_struct *task, unsigned long filter_off,
> + void __user *data)
> +{
> + struct seccomp_filter *filter;
> + struct sock_fprog_kern *fprog;
> + long ret;
> + unsigned long count = 0;
> +
> + if (!capable(CAP_SYS_ADMIN) ||
> + current->seccomp.mode != SECCOMP_MODE_DISABLED) {
> + return -EACCES;
> + }
> +
> + spin_lock_irq(&task->sighand->siglock);
> + if (task->seccomp.mode != SECCOMP_MODE_FILTER) {
> + ret = -EINVAL;
> + goto out_task;
> + }
> +
> + filter = task->seccomp.filter;
> + while (filter) {
> + filter = filter->prev;
> + count++;
> + }
> +
> + if (filter_off >= count) {
> + ret = -ENOENT;
> + goto out_task;
> + }
> + count -= filter_off;
> +
> + filter = task->seccomp.filter;
> + while (filter && count > 1) {
> + filter = filter->prev;
> + count--;
> + }
> +
> + if (WARN_ON(count != 1)) {
> + /* The filter tree shouldn't shrink while we're using it. */
> + ret = -ENOENT;
> + goto out_task;
> + }
> +
> + fprog = filter->prog->orig_prog;
> + if (!fprog) {
> + /* This must be a new non-cBPF filter, since we save every
> + * every cBPF filter's orig_prog above when
> + * CONFIG_CHECKPOINT_RESTORE is enabled.
> + */
> + ret = -EMEDIUMTYPE;
> + goto out_task;
> + }
> +
> + ret = fprog->len;
> + if (!data)
> + goto out_task;
> +
> + if (copy_to_user(data, fprog->filter, bpf_classic_proglen(fprog))) {
> + ret = -EFAULT;
> + goto out_task;
> + }
Oh wait, I didn't notice this when I looked at v7.
No, you can't do copy_to_user() from atomic context. You need to pin this
filter, drop the lock/irq, then copy_to_user().
Oleg.
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