Re: [PATCH 1/2] procfs: use an enum for possible hidepid values

Kees Cook
2016-11-15T23:27:33Z

On Thu, Nov 3, 2016 at 8:49 AM, Kees Cook <keescook@chromium.org> wrote:
> On Thu, Nov 3, 2016 at 9:30 AM, Lafcadio Wluiki <wluikil@gmail.com> wrote:
>> (Third, rebased submission, since first two submissions yielded no replies.)
>
> Hm, I didn't see this series before, for some reason.
>
>> Previously, the hidepid parameter was checked by comparing literal
>> integers 0, 1, 2. Let's add a proper enum for this, to make the checking
>> more expressive:
>>
>> 0 → HIDEPID_OFF
>> 1 → HIDEPID_NO_ACCESS
>> 2 → HIDEPID_INVISIBLE
>>
>> This changes the internal labelling only, the userspace-facing interface
>> remains unmodified, and still works with literal integers 0, 1, 2.
>>
>> No functional changes.
>>
>> Signed-off-by: Lafcadio Wluiki <wluikil@gmail.com>
>
> Yup, this is good. Dropping literals is always preferred. :)
>
> Acked-by: Kees Cook <keescook@chromium.org>

Hi,

Friendly ping to Andrew for picking up this clean-up for -mm. (Though
not yet the 2/2 patch, as it still has some unanswered questions...)

-Kees

>
> -Kees
>
>> ---
>> fs/proc/base.c | 8 ++++----
>> fs/proc/inode.c | 2 +-
>> fs/proc/root.c | 3 ++-
>> include/linux/pid_namespace.h | 6 ++++++
>> 4 files changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index ca651ac..ae5e13c 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -726,11 +726,11 @@ static int proc_pid_permission(struct inode *inode, int mask)
>> task = get_proc_task(inode);
>> if (!task)
>> return -ESRCH;
>> - has_perms = has_pid_permissions(pid, task, 1);
>> + has_perms = has_pid_permissions(pid, task, HIDEPID_NO_ACCESS);
>> put_task_struct(task);
>>
>> if (!has_perms) {
>> - if (pid->hide_pid == 2) {
>> + if (pid->hide_pid == HIDEPID_INVISIBLE) {
>> /*
>> * Let's make getdents(), stat(), and open()
>> * consistent with each other. If a process
>> @@ -1720,7 +1720,7 @@ int pid_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
>> stat->gid = GLOBAL_ROOT_GID;
>> task = pid_task(proc_pid(inode), PIDTYPE_PID);
>> if (task) {
>> - if (!has_pid_permissions(pid, task, 2)) {
>> + if (!has_pid_permissions(pid, task, HIDEPID_INVISIBLE)) {
>> rcu_read_unlock();
>> /*
>> * This doesn't prevent learning whether PID exists,
>> @@ -3181,7 +3181,7 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx)
>> iter.tgid += 1, iter = next_tgid(ns, iter)) {
>> char name[PROC_NUMBUF];
>> int len;
>> - if (!has_pid_permissions(ns, iter.task, 2))
>> + if (!has_pid_permissions(ns, iter.task, HIDEPID_INVISIBLE))
>> continue;
>>
>> len = snprintf(name, sizeof(name), "%d", iter.tgid);
>> diff --git a/fs/proc/inode.c b/fs/proc/inode.c
>> index e69ebe6..872325e 100644
>> --- a/fs/proc/inode.c
>> +++ b/fs/proc/inode.c
>> @@ -106,7 +106,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root)
>>
>> if (!gid_eq(pid->pid_gid, GLOBAL_ROOT_GID))
>> seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, pid->pid_gid));
>> - if (pid->hide_pid != 0)
>> + if (pid->hide_pid != HIDEPID_OFF)
>> seq_printf(seq, ",hidepid=%u", pid->hide_pid);
>>
>> return 0;
>> diff --git a/fs/proc/root.c b/fs/proc/root.c
>> index 8d3e484..2989731 100644
>> --- a/fs/proc/root.c
>> +++ b/fs/proc/root.c
>> @@ -58,7 +58,8 @@ int proc_parse_options(char *options, struct pid_namespace *pid)
>> case Opt_hidepid:
>> if (match_int(&args[0], &option))
>> return 0;
>> - if (option < 0 || option > 2) {
>> + if (option < HIDEPID_OFF ||
>> + option > HIDEPID_INVISIBLE) {
>> pr_err("proc: hidepid value must be between 0 and 2.\n");
>> return 0;
>> }
>> diff --git a/include/linux/pid_namespace.h b/include/linux/pid_namespace.h
>> index 34cce96..c2a989d 100644
>> --- a/include/linux/pid_namespace.h
>> +++ b/include/linux/pid_namespace.h
>> @@ -21,6 +21,12 @@ struct pidmap {
>>
>> struct fs_pin;
>>
>> +enum { /* definitions for pid_namespace's hide_pid field */
>> + HIDEPID_OFF = 0,
>> + HIDEPID_NO_ACCESS = 1,
>> + HIDEPID_INVISIBLE = 2,
>> +};
>> +
>> struct pid_namespace {
>> struct kref kref;
>> struct pidmap pidmap[PIDMAP_ENTRIES];
>> --
>> 2.7.4
>>
>
>
>
> --
> Kees Cook
> Nexus Security

--
Kees Cook
Nexus Security