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Message-Id: <20200423200316.164518-5-gladkov.alexey@gmail.com>
Date: Thu, 23 Apr 2020 22:03:12 +0200
From: Alexey Gladkov <gladkov.alexey@...il.com>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linux API <linux-api@...r.kernel.org>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>,
Linux Security Module <linux-security-module@...r.kernel.org>,
Akinobu Mita <akinobu.mita@...il.com>,
Alexander Viro <viro@...iv.linux.org.uk>,
Alexey Dobriyan <adobriyan@...il.com>,
Alexey Gladkov <legion@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...nel.org>,
Daniel Micay <danielmicay@...il.com>,
Djalal Harouni <tixxdz@...il.com>,
"Dmitry V . Levin" <ldv@...linux.org>,
"Eric W . Biederman" <ebiederm@...ssion.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...nel.org>,
"J . Bruce Fields" <bfields@...ldses.org>,
Jeff Layton <jlayton@...chiereds.net>,
Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>,
David Howells <dhowells@...hat.com>
Subject: [PATCH v13 4/8] 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.
Signed-off-by: Djalal Harouni <tixxdz@...il.com>
Signed-off-by: Alexey Gladkov <gladkov.alexey@...il.com>
Reviewed-by: Alexey Dobriyan <adobriyan@...il.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
fs/proc/base.c | 15 +++++++++++++++
fs/proc/root.c | 13 ++++++++++---
include/linux/proc_fs.h | 1 +
3 files changed, 26 insertions(+), 3 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 93b5d05c142c..a52a91e90c25 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -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;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 208989274923..8f23b951d685 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c
@@ -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:
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 1b98a41fdd8a..5bdc117ae947 100644
--- a/include/linux/proc_fs.h
+++ b/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 {
--
2.25.3
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