The patch titled
Subject: proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option
has been added to the -mm tree. Its filename is
proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid=4-mount-option.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid%3D4-mount-option.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid%3D4-mount-option.patch
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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Alexey Gladkov <gladkov.alexey@xxxxxxxxx>
Subject: proc: instantiate only pids that we can ptrace on 'hidepid=4' mount option
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.
Link: http://lkml.kernel.org/r/20200419141057.621356-4-gladkov.alexey@xxxxxxxxx
Signed-off-by: Djalal Harouni <tixxdz@xxxxxxxxx>
Signed-off-by: Alexey Gladkov <gladkov.alexey@xxxxxxxxx>
Reviewed-by: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Akinobu Mita <akinobu.mita@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Daniel Micay <danielmicay@xxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: "Dmitry V . Levin" <ldv@xxxxxxxxxxxx>
Cc: "Eric W . Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "J . Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 15 +++++++++++++++
fs/proc/root.c | 13 ++++++++++---
include/linux/proc_fs.h | 1 +
3 files changed, 26 insertions(+), 3 deletions(-)
--- a/fs/proc/base.c~proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid=4-mount-option
+++ a/fs/proc/base.c
@@ -701,6 +701,14 @@ static bool has_pid_permissions(struct p
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))
@@ -3331,7 +3339,14 @@ struct dentry *proc_pid_lookup(struct de
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;
--- a/fs/proc/root.c~proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid=4-mount-option
+++ a/fs/proc/root.c
@@ -47,6 +47,14 @@ static const struct fs_parameter_spec pr
{}
};
+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_co
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:
--- a/include/linux/proc_fs.h~proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid=4-mount-option
+++ a/include/linux/proc_fs.h
@@ -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 {
_
Patches currently in -mm which might be from gladkov.alexey@xxxxxxxxx are
proc-rename-struct-proc_fs_info-to-proc_fs_opts.patch
proc-allow-to-mount-many-instances-of-proc-in-one-pid-namespace.patch
proc-instantiate-only-pids-that-we-can-ptrace-on-hidepid=4-mount-option.patch
proc-add-option-to-mount-only-a-pids-subset.patch
docs-proc-add-documentation-for-hidepid=4-and-subset=pid-options-and-new-mount-behavior.patch
proc-use-human-readable-values-for-hidepid.patch
proc-use-named-enums-for-better-readability.patch
