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Message-ID: <20150205023410.8382.13695.stgit@pluto.fritz.box>
Date: Thu, 05 Feb 2015 10:34:11 +0800
From: Ian Kent <ikent@...hat.com>
To: Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: David Howells <dhowells@...hat.com>,
Oleg Nesterov <onestero@...hat.com>,
Trond Myklebust <trond.myklebust@...marydata.com>,
"J. Bruce Fields" <bfields@...ldses.org>,
Benjamin Coddington <bcodding@...hat.com>,
Al Viro <viro@...IV.linux.org.uk>,
Jeff Layton <jeff.layton@...marydata.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [RFC PATCH 3/8] kmod - teach call_usermodehelper() to use a
namespace
The call_usermodehelper() function executes all binaries in the
global "init" root context. This doesn't allow a binary to be run
within a namespace (eg. the namespace of a container).
Both containerized NFS client and NFS server need the ability to
execute a binary in a container's context. To do this use the init
process of the callers environment is used to setup the namespaces
in the same way the root init process is used otherwise.
Signed-off-by: Ian Kent <ikent@...hat.com>
Cc: Benjamin Coddington <bcodding@...hat.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
Cc: J. Bruce Fields <bfields@...ldses.org>
Cc: David Howells <dhowells@...hat.com>
Cc: Trond Myklebust <trond.myklebust@...marydata.com>
Cc: Oleg Nesterov <onestero@...hat.com>
Cc: Eric W. Biederman <ebiederm@...ssion.com>
Cc: Jeff Layton <jeff.layton@...marydata.com>
---
include/linux/kmod.h | 16 +++++++
kernel/kmod.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 128 insertions(+), 3 deletions(-)
diff --git a/include/linux/kmod.h b/include/linux/kmod.h
index 15bdeed..b0f1b3c 100644
--- a/include/linux/kmod.h
+++ b/include/linux/kmod.h
@@ -52,6 +52,7 @@ struct file;
#define UMH_WAIT_EXEC 1 /* wait for the exec, but not the process */
#define UMH_WAIT_PROC 2 /* wait for the process to complete */
#define UMH_KILLABLE 4 /* wait for EXEC/PROC killable */
+#define UMH_USE_NS 8 /* exec using caller's init namespace */
struct subprocess_info {
struct work_struct work;
@@ -69,6 +70,21 @@ struct subprocess_info {
extern int
call_usermodehelper(char *path, char **argv, char **envp, int flags);
+#if !defined(CONFIG_PROC_FS) || !defined(CONFIG_NAMESPACES)
+inline struct task_struct *umh_get_init_task(void)
+{
+ return ERR_PTR(-ENOTSUP);
+}
+
+inline int umh_enter_ns(struct task_struct *tsk, struct cred *new)
+{
+ return -ENOTSUP;
+}
+#else
+struct task_struct *umh_get_init_pid(void);
+int umh_enter_ns(struct task_struct *tsk, struct cred *new);
+#endif
+
extern struct subprocess_info *
call_usermodehelper_setup(char *path, char **argv, char **envp, gfp_t gfp_mask,
int (*init)(struct subprocess_info *info, struct cred *new),
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 14c0188..4c649d6 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -582,6 +582,98 @@ unlock:
}
EXPORT_SYMBOL(call_usermodehelper_exec);
+#if defined(CONFIG_PROC_FS) && defined(CONFIG_NAMESPACES)
+#define NS_PATH_MAX 35
+#define NS_PATH_FMT "%lu/ns/%s"
+
+/* Note namespace name order is significant */
+static const char *ns_names[] = { "user", "ipc", "uts", "net", "pid", "mnt", NULL };
+
+struct task_struct *umh_get_init_pid(void)
+{
+ struct task_struct *tsk;
+
+ rcu_read_lock();
+ tsk = find_task_by_vpid(1);
+ if (tsk)
+ get_task_struct(tsk);
+ rcu_read_unlock();
+ if (!tsk)
+ return ERR_PTR(-ESRCH);
+
+ return tsk;
+}
+EXPORT_SYMBOL(umh_get_init_pid);
+
+int umh_enter_ns(struct task_struct *tsk, struct cred *new)
+{
+ char path[NS_PATH_MAX];
+ struct vfsmount *mnt;
+ const char *name;
+ pid_t pid;
+ int err = 0;
+
+ pid = task_pid_nr(tsk);
+
+ /*
+ * The user mode thread runner runs in the root init namespace
+ * so it will see all system pids.
+ */
+ mnt = task_active_pid_ns(current)->proc_mnt;
+
+ for (name = ns_names[0]; *name; name++) {
+ struct file *this;
+ int len;
+
+ len = snprintf(path,
+ NS_PATH_MAX, NS_PATH_FMT,
+ (unsigned long) pid, name);
+ if (len >= NS_PATH_MAX) {
+ err = -ENAMETOOLONG;
+ break;
+ }
+
+ this = file_open_root(mnt->mnt_root, mnt, path, O_RDONLY);
+ if (unlikely(IS_ERR(this))) {
+ err = PTR_ERR(this);
+ break;
+ }
+
+ err = setns_inode(file_inode(this), 0);
+ fput(this);
+ if (err)
+ break;
+ }
+
+ return err;
+}
+EXPORT_SYMBOL(umh_enter_ns);
+
+static int umh_set_ns(struct subprocess_info *info, struct cred *new)
+{
+ struct task_struct *tsk = info->data;
+
+ return umh_enter_ns(tsk, new);
+}
+
+static void umh_free_ns(struct subprocess_info *info)
+{
+ struct task_struct *tsk = info->data;
+
+ if (tsk)
+ put_task_struct(tsk);
+}
+#else
+static int umh_set_ns(struct subprocess_info *info, struct cred *new)
+{
+ return 0;
+}
+
+static void umh_free_ns(struct subprocess_info *info)
+{
+}
+#endif
+
/**
* call_usermodehelper() - prepare and start a usermode application
* @path: path to usermode executable
@@ -599,11 +691,28 @@ int call_usermodehelper(char *path, char **argv, char **envp, int flags)
{
struct subprocess_info *info;
gfp_t gfp_mask = (flags == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
+ unsigned int use_ns = flags & UMH_USE_NS;
+ struct task_struct *tsk = NULL;
+
+ if (use_ns) {
+ tsk = umh_get_init_pid();
+ if (IS_ERR(tsk))
+ return PTR_ERR(tsk);
+ }
- info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
- NULL, NULL, NULL);
- if (info == NULL)
+ if (!tsk)
+ info = call_usermodehelper_setup(path, argv, envp,
+ gfp_mask, NULL, NULL, NULL);
+ else {
+ info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
+ umh_set_ns, umh_free_ns,
+ tsk);
+ }
+ if (info == NULL) {
+ if (tsk)
+ put_task_struct(tsk);
return -ENOMEM;
+ }
return call_usermodehelper_exec(info, flags);
}
--
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