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proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option

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If "hidepid=4" mount option is set then do not instantiate pids that
we can not ptrace. "hidepid=4" means that procfs should only contain
pids that the caller can ptrace.

Signed-off-by: Djalal Harouni <tixxdz@gmail.com>
Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
Reviewed-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
This commit is contained in:
Alexey Gladkov 2020-04-19 16:10:53 +02:00 committed by Eric W. Biederman
parent fa10fed30f
commit 24a71ce5c4
3 changed files with 26 additions and 3 deletions
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15
fs/proc/base.c
View File

@ -701,6 +701,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info,
struct task_struct *task,
int hide_pid_min)
{
/*
* If 'hidpid' mount option is set force a ptrace check,
* we indicate that we are using a filesystem syscall
* by passing PTRACE_MODE_READ_FSCREDS
*/
if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE)
return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
if (fs_info->hide_pid < hide_pid_min)
return true;
if (in_group_p(fs_info->pid_gid))
@ -3319,7 +3327,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
if (!task)
goto out;
/* Limit procfs to only ptraceable tasks */
if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE) {
if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
goto out_put_task;
}
result = proc_pid_instantiate(dentry, task, NULL);
out_put_task:
put_task_struct(task);
out:
return result;

13
fs/proc/root.c
View File

@ -47,6 +47,14 @@ static const struct fs_parameter_spec proc_fs_parameters[] = {
{}
};
static inline int valid_hidepid(unsigned int value)
{
return (value == HIDEPID_OFF ||
value == HIDEPID_NO_ACCESS ||
value == HIDEPID_INVISIBLE ||
value == HIDEPID_NOT_PTRACEABLE);
}
static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct proc_fs_context *ctx = fc->fs_private;
@ -63,10 +71,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param)
break;
case Opt_hidepid:
if (!valid_hidepid(result.uint_32))
return invalf(fc, "proc: unknown value of hidepid.\n");
ctx->hidepid = result.uint_32;
if (ctx->hidepid < HIDEPID_OFF ||
ctx->hidepid > HIDEPID_INVISIBLE)
return invalfc(fc, "hidepid value must be between 0 and 2.\n");
break;
default:

1
include/linux/proc_fs.h
View File

@ -47,6 +47,7 @@ enum {
HIDEPID_OFF = 0,
HIDEPID_NO_ACCESS = 1,
HIDEPID_INVISIBLE = 2,
HIDEPID_NOT_PTRACEABLE = 4, /* Limit pids to only ptraceable pids */
};
struct proc_fs_info {