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Message-ID: <20071016193850.GA5418@roonstrasse.net>
Date: Tue, 16 Oct 2007 21:38:50 +0200
From: Max Kellermann <mk@...all.com>
To: chrisw@...s-sol.org, linux-security-module@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH] /proc Security Hooks
Add two LSM hooks for limiting access to the proc file system.
security_proc_task() defines the visibility of tasks in /proc.
security_proc_generic() lets the LSM define who will see "generic"
proc entries (see fs/proc/generic.c).
This patch attempts to unify duplicated code found in modules like
Linux VServer.
Signed-off-by: Max Kellermann <mk@...all.com>
---
fs/proc/base.c | 9 +++++++++
fs/proc/generic.c | 15 +++++++++++++++
include/linux/security.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++
security/Kconfig | 8 ++++++++
security/dummy.c | 16 ++++++++++++++++
5 files changed, 94 insertions(+), 0 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 19489b0..a6ebe2d 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -2317,6 +2317,10 @@ int proc_pid_readdir(struct file * filp, void * dirent, filldir_t filldir)
put_task_struct(task), task = next_tgid(tgid + 1)) {
tgid = task->pid;
filp->f_pos = tgid + TGID_OFFSET;
+#ifdef CONFIG_SECURITY_PROC
+ if (security_proc_task(task) != 0)
+ continue;
+#endif
if (proc_pid_fill_cache(filp, dirent, filldir, task, tgid) < 0) {
put_task_struct(task);
goto out;
@@ -2453,6 +2457,11 @@ static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry
goto out;
if (leader->tgid != task->tgid)
goto out_drop_task;
+#ifdef CONFIG_SECURITY_PROC
+ result = ERR_PTR(security_proc_task(task));
+ if (IS_ERR(result))
+ goto out_drop_task;
+#endif
result = proc_task_instantiate(dir, dentry, task, NULL);
out_drop_task:
diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index b5e7155..7b17ec3 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -21,6 +21,9 @@
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
+#ifdef CONFIG_SECURITY_PROC
+#include <linux/security.h>
+#endif
#include <asm/uaccess.h>
#include "internal.h"
@@ -400,6 +403,11 @@ struct dentry *proc_lookup(struct inode * dir, struct dentry *dentry, struct nam
unsigned int ino = de->low_ino;
de_get(de);
+#ifdef CONFIG_SECURITY_PROC
+ error = security_proc_generic(de);
+ if (error != 0)
+ break;
+#endif
spin_unlock(&proc_subdir_lock);
error = -EINVAL;
inode = proc_get_inode(dir->i_sb, ino, de);
@@ -483,6 +491,10 @@ int proc_readdir(struct file * filp,
/* filldir passes info to user space */
de_get(de);
+#ifdef CONFIG_SECURITY_PROC
+ if (security_proc_generic(de) != 0)
+ goto skip;
+#endif
spin_unlock(&proc_subdir_lock);
if (filldir(dirent, de->name, de->namelen, filp->f_pos,
de->low_ino, de->mode >> 12) < 0) {
@@ -490,6 +502,9 @@ int proc_readdir(struct file * filp,
goto out;
}
spin_lock(&proc_subdir_lock);
+#ifdef CONFIG_SECURITY_PROC
+ skip:
+#endif
filp->f_pos++;
next = de->next;
de_put(de);
diff --git a/include/linux/security.h b/include/linux/security.h
index 1a15526..3fbeacf 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -68,6 +68,10 @@ struct xfrm_policy;
struct xfrm_state;
struct xfrm_user_sec_ctx;
+#ifdef CONFIG_SECURITY_PROC
+struct proc_dir_entry;
+#endif
+
extern int cap_netlink_send(struct sock *sk, struct sk_buff *skb);
extern int cap_netlink_recv(struct sk_buff *skb, int cap);
@@ -915,6 +919,17 @@ struct request_sock;
* Return 1 if permission granted, 0 if permission denied and -ve it the
* normal permissions model should be effected.
*
+ * Security hooks affecting proc visibility
+ *
+ * @proc_task:
+ * Determines whether a task is visible.
+ * @task the requested task
+ * Return 0 if task is visible, -ENOENT if not, or -errno on other errors
+ * @proc_generic:
+ * Determines whether a generic proc entry is visible
+ * @de the requested proc_dir_entry structure
+ * Return 0 if entry is visible, -ENOENT if not, or -errno on other errors
+ *
* Security hooks affecting all System V IPC operations.
*
* @ipc_permission:
@@ -1399,6 +1414,11 @@ struct security_operations {
#endif /* CONFIG_KEYS */
+ #ifdef CONFIG_SECURITY_PROC
+ int (*proc_task)(struct task_struct *task);
+ int (*proc_generic)(struct proc_dir_entry *de);
+ #endif
+
};
/* global variables */
@@ -3314,5 +3334,31 @@ static inline int security_key_permission(key_ref_t key_ref,
#endif
#endif /* CONFIG_KEYS */
+#ifdef CONFIG_SECURITY_PROC
+#ifdef CONFIG_SECURITY
+static inline int security_proc_task(struct task_struct *task)
+{
+ return security_ops->proc_task(task);
+}
+
+static inline int security_proc_generic(struct proc_dir_entry *de)
+{
+ return security_ops->proc_generic(de);
+}
+
+#else
+
+static inline int security_proc_task(struct task_struct *task)
+{
+ return 0;
+}
+
+static inline int security_proc_generic(struct proc_dir_entry *de)
+{
+ return 0;
+}
+#endif
+#endif
+
#endif /* ! __LINUX_SECURITY_H */
diff --git a/security/Kconfig b/security/Kconfig
index 460e5c9..bd6ad4b 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -73,6 +73,14 @@ config SECURITY_NETWORK_XFRM
IPSec.
If you are unsure how to answer this question, answer N.
+config SECURITY_PROC
+ bool "/proc Security Hooks"
+ depends on PROC_FS && SECURITY
+ help
+ This enables the /proc security hooks.
+ These allow an LSM to hide nodes in the proc filesystem.
+ If you are unsure how to answer this question, answer N.
+
config SECURITY_CAPABILITIES
tristate "Default Linux Capabilities"
depends on SECURITY
diff --git a/security/dummy.c b/security/dummy.c
index 853ec22..3ec57be 100644
--- a/security/dummy.c
+++ b/security/dummy.c
@@ -949,6 +949,18 @@ static inline int dummy_key_permission(key_ref_t key_ref,
}
#endif /* CONFIG_KEYS */
+#ifdef CONFIG_SECURITY_PROC
+static int dummy_proc_task(struct task_struct *task)
+{
+ return 0;
+}
+
+static int dummy_proc_generic(struct proc_dir_entry *de)
+{
+ return 0;
+}
+#endif
+
struct security_operations dummy_security_ops;
#define set_to_dummy_if_null(ops, function) \
@@ -1131,6 +1143,10 @@ void security_fixup_ops (struct security_operations *ops)
set_to_dummy_if_null(ops, key_free);
set_to_dummy_if_null(ops, key_permission);
#endif /* CONFIG_KEYS */
+#ifdef CONFIG_SECURITY_PROC
+ set_to_dummy_if_null(ops, proc_task);
+ set_to_dummy_if_null(ops, proc_generic);
+#endif
}
-
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