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

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Date:   Tue, 15 Nov 2016 15:27:28 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Lafcadio Wluiki <wluikil@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] procfs: use an enum for possible hidepid values

On Thu, Nov 3, 2016 at 8:49 AM, Kees Cook <keescook@...omium.org> wrote:
> On Thu, Nov 3, 2016 at 9:30 AM, Lafcadio Wluiki <wluikil@...il.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@...il.com>
>
> Yup, this is good. Dropping literals is always preferred. :)
>
> Acked-by: Kees Cook <keescook@...omium.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