[PATCH v6 03/11] umh: add dirfd parameter

["Thomas Weißschuh" <thomas.weissschuh@linutronix.de>]

Allow callers to specify the directory against which to resolve the
helper's filename. Enables the running of helpers from private mounts.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
---
 fs/coredump.c               | 2 +-
 include/linux/umh.h         | 3 ++-
 kernel/module/kmod.c        | 2 +-
 kernel/umh.c                | 9 ++++++---
 lib/kobject_uevent.c        | 2 +-
 security/keys/request_key.c | 2 +-
 6 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/fs/coredump.c b/fs/coredump.c
index bb6fdb1f458e..45df2387be3d 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1015,7 +1015,7 @@ static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm,
 		helper_argv[argi] = cn->corename + argv[argi];
 	helper_argv[argi] = NULL;
 
-	sub_info = call_usermodehelper_setup(helper_argv[0], helper_argv, NULL,
+	sub_info = call_usermodehelper_setup(AT_FDCWD, helper_argv[0], helper_argv, NULL,
 					     GFP_KERNEL, umh_coredump_setup,
 					     NULL, cprm);
 	if (!sub_info)
diff --git a/include/linux/umh.h b/include/linux/umh.h
index daa6a7048c11..6670b9ff85d4 100644
--- a/include/linux/umh.h
+++ b/include/linux/umh.h
@@ -20,6 +20,7 @@ struct file;
 struct subprocess_info {
 	struct work_struct work;
 	struct completion *complete;
+	int dirfd;
 	const char *path;
 	char **argv;
 	char **envp;
@@ -34,7 +35,7 @@ extern int
 call_usermodehelper(const char *path, char **argv, char **envp, int wait);
 
 extern struct subprocess_info *
-call_usermodehelper_setup(const char *path, char **argv, char **envp,
+call_usermodehelper_setup(int dirfd, const char *path, char **argv, char **envp,
 			  gfp_t gfp_mask,
 			  int (*init)(struct subprocess_info *info, struct cred *new),
 			  void (*cleanup)(struct subprocess_info *), void *data);
diff --git a/kernel/module/kmod.c b/kernel/module/kmod.c
index a25dccdf7aa7..a85c57a707af 100644
--- a/kernel/module/kmod.c
+++ b/kernel/module/kmod.c
@@ -95,7 +95,7 @@ static int call_modprobe(char *orig_module_name, int wait)
 	argv[3] = module_name;	/* check free_modprobe_argv() */
 	argv[4] = NULL;
 
-	info = call_usermodehelper_setup(modprobe_path, argv, envp, GFP_KERNEL,
+	info = call_usermodehelper_setup(AT_FDCWD, modprobe_path, argv, envp, GFP_KERNEL,
 					 NULL, free_modprobe_argv, NULL);
 	if (!info)
 		goto free_module_name;
diff --git a/kernel/umh.c b/kernel/umh.c
index bab134fa8c36..5cdcba6005d9 100644
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -106,7 +106,7 @@ static int call_usermodehelper_exec_async(void *data)
 	commit_creds(new);
 
 	wait_for_initramfs();
-	retval = kernel_execve(AT_FDCWD, sub_info->path,
+	retval = kernel_execve(sub_info->dirfd, sub_info->path,
 			       (const char *const *)sub_info->argv,
 			       (const char *const *)sub_info->envp);
 out:
@@ -331,6 +331,7 @@ static void helper_unlock(void)
 
 /**
  * call_usermodehelper_setup - prepare to call a usermode helper
+ * @dirfd: directory to resolve path against
  * @path: path to usermode executable
  * @argv: arg vector for process
  * @envp: environment for process
@@ -352,7 +353,7 @@ static void helper_unlock(void)
  * Function must be runnable in either a process context or the
  * context in which call_usermodehelper_exec is called.
  */
-struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
+struct subprocess_info *call_usermodehelper_setup(int dirfd, const char *path, char **argv,
 		char **envp, gfp_t gfp_mask,
 		int (*init)(struct subprocess_info *info, struct cred *new),
 		void (*cleanup)(struct subprocess_info *info),
@@ -366,8 +367,10 @@ struct subprocess_info *call_usermodehelper_setup(const char *path, char **argv,
 	INIT_WORK(&sub_info->work, call_usermodehelper_exec_work);
 
 #ifdef CONFIG_STATIC_USERMODEHELPER
+	sub_info->dirfd = AT_FDCWD;
 	sub_info->path = CONFIG_STATIC_USERMODEHELPER_PATH;
 #else
+	sub_info->dirfd = dirfd;
 	sub_info->path = path;
 #endif
 	sub_info->argv = argv;
@@ -484,7 +487,7 @@ int call_usermodehelper(const char *path, char **argv, char **envp, int wait)
 	struct subprocess_info *info;
 	gfp_t gfp_mask = (wait == UMH_NO_WAIT) ? GFP_ATOMIC : GFP_KERNEL;
 
-	info = call_usermodehelper_setup(path, argv, envp, gfp_mask,
+	info = call_usermodehelper_setup(AT_FDCWD, path, argv, envp, gfp_mask,
 					 NULL, NULL, NULL);
 	if (info == NULL)
 		return -ENOMEM;
diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
index ddbc4d7482d2..426ac83f1d2a 100644
--- a/lib/kobject_uevent.c
+++ b/lib/kobject_uevent.c
@@ -628,7 +628,7 @@ int kobject_uevent_env(struct kobject *kobj, enum kobject_action action,
 			goto exit;
 
 		retval = -ENOMEM;
-		info = call_usermodehelper_setup(env->argv[0], env->argv,
+		info = call_usermodehelper_setup(AT_FDCWD, env->argv[0], env->argv,
 						 env->envp, GFP_KERNEL,
 						 NULL, cleanup_uevent_env, env);
 		if (info) {
diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index a7673ad86d18..f6f3d4bc0bda 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -101,7 +101,7 @@ static int call_usermodehelper_keys(const char *path, char **argv, char **envp,
 {
 	struct subprocess_info *info;
 
-	info = call_usermodehelper_setup(path, argv, envp, GFP_KERNEL,
+	info = call_usermodehelper_setup(AT_FDCWD, path, argv, envp, GFP_KERNEL,
 					  umh_keys_init, umh_keys_cleanup,
 					  session_keyring);
 	if (!info)

-- 
2.53.0