netdev - Re: [PATCH bpf-next 2/2] selftests/bpf: add tests for bpf_find

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Message-ID: <25320fdb-bf37-9fd2-869c-72657de8e9a8@iogearbox.net>
Date:   Mon, 1 Nov 2021 23:26:36 +0100
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Song Liu <songliubraving@...com>, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Cc:     ast@...nel.org, andrii@...nel.org, kernel-team@...com,
        kpsingh@...nel.org
Subject: Re: [PATCH bpf-next 2/2] selftests/bpf: add tests for bpf_find_vma

On 10/28/21 12:00 AM, Song Liu wrote:
[...]
> +static __u64
> +check_vma(struct task_struct *task, struct vm_area_struct *vma,
> +	  struct callback_ctx *data)
> +{
> +	if (vma->vm_file)
> +		bpf_probe_read_kernel_str(d_iname, DNAME_INLINE_LEN - 1,
> +					  vma->vm_file->f_path.dentry->d_iname);
> +
> +	/* check for VM_EXEC */
> +	if (vma->vm_flags & VM_EXEC)
> +		found_vm_exec = 1;
> +

Could you also add test cases that verifier will reject write attempts to task/vma
for the callback?

> +	return 0;
> +}
> +
> +SEC("kprobe/__x64_sys_getpgid")
> +int handle_getpid(void)
> +{
> +	struct task_struct *task = bpf_get_current_task_btf();
> +	struct callback_ctx data = {0};
> +
> +	if (task->pid != target_pid)
> +		return 0;
> +
> +	find_addr_ret = bpf_find_vma(task, addr, check_vma, &data, 0);
> +
> +	/* this should return -ENOENT */
> +	find_zero_ret = bpf_find_vma(task, 0, check_vma, &data, 0);
> +	return 0;
> +}
> +
> +SEC("perf_event")
> +int handle_pe(void)
> +{
> +	struct task_struct *task = bpf_get_current_task_btf();
> +	struct callback_ctx data = {0};
> +
> +	if (task->pid != target_pid)
> +		return 0;
> +
> +	find_addr_ret = bpf_find_vma(task, addr, check_vma, &data, 0);
> +
> +	/* In NMI, this should return -EBUSY, as the previous call is using
> +	 * the irq_work.
> +	 */
> +	find_zero_ret = bpf_find_vma(task, 0, check_vma, &data, 0);
> +	return 0;
> +}
>