Merge tag 'v3.6-rc1' into staging/for_v3.6

Linux 3.6-rc1

* tag 'v3.6-rc1': (18733 commits)
  Linux 3.6-rc1
  mm: remove node_start_pfn checking in new WARN_ON for now
  ARM: mmp: add missing irqs.h
  arm: mvebu: fix typo in .dtsi comment for Armada XP SoCs
  ARM: PRIMA2: delete redundant codes to restore LATCHED when timer resumes
  libceph: fix crypto key null deref, memory leak
  ceph: simplify+fix atomic_open
  sh: explicitly include sh_dma.h in setup-sh7722.c
  um: Add arch/x86/um to MAINTAINERS
  um: pass siginfo to guest process
  um: fix ubd_file_size for read-only files
  md/dm-raid: DM_RAID should select MD_RAID10
  md/raid1: submit IO from originating thread instead of md thread.
  raid5: raid5d handle stripe in batch way
  raid5: make_request use batch stripe release
  um: pull interrupt_end() into userspace()
  um: split syscall_trace(), pass pt_regs to it
  um: switch UPT_SET_RETURN_VALUE and regs_return_value to pt_regs
  MIPS: Loongson 2: Sort out clock managment.
  locks: remove unused lm_release_private
  ...

1 files changed, 59 insertions, 8 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index 05698a7415fe..6f99aead66c6 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -45,6 +45,13 @@ extern int max_threads;
 
 static struct workqueue_struct *khelper_wq;
 
+/*
+ * kmod_thread_locker is used for deadlock avoidance.  There is no explicit
+ * locking to protect this global - it is private to the singleton khelper
+ * thread and should only ever be modified by that thread.
+ */
+static const struct task_struct *kmod_thread_locker;
+
 #define CAP_BSET	(void *)1
 #define CAP_PI		(void *)2
 
@@ -221,13 +228,19 @@ fail:
 	return 0;
 }
 
-void call_usermodehelper_freeinfo(struct subprocess_info *info)
+static int call_helper(void *data)
+{
+	/* Worker thread started blocking khelper thread. */
+	kmod_thread_locker = current;
+	return ____call_usermodehelper(data);
+}
+
+static void call_usermodehelper_freeinfo(struct subprocess_info *info)
 {
 	if (info->cleanup)
 		(*info->cleanup)(info);
 	kfree(info);
 }
-EXPORT_SYMBOL(call_usermodehelper_freeinfo);
 
 static void umh_complete(struct subprocess_info *sub_info)
 {
@@ -296,9 +309,12 @@ static void __call_usermodehelper(struct work_struct *work)
 	if (wait == UMH_WAIT_PROC)
 		pid = kernel_thread(wait_for_helper, sub_info,
 				    CLONE_FS | CLONE_FILES | SIGCHLD);
-	else
-		pid = kernel_thread(____call_usermodehelper, sub_info,
+	else {
+		pid = kernel_thread(call_helper, sub_info,
 				    CLONE_VFORK | SIGCHLD);
+		/* Worker thread stopped blocking khelper thread. */
+		kmod_thread_locker = NULL;
+	}
 
 	switch (wait) {
 	case UMH_NO_WAIT:
@@ -410,7 +426,7 @@ EXPORT_SYMBOL_GPL(usermodehelper_read_unlock);
 
 /**
  * __usermodehelper_set_disable_depth - Modify usermodehelper_disabled.
- * depth: New value to assign to usermodehelper_disabled.
+ * @depth: New value to assign to usermodehelper_disabled.
  *
  * Change the value of usermodehelper_disabled (under umhelper_sem locked for
  * writing) and wakeup tasks waiting for it to change.
@@ -479,6 +495,7 @@ static void helper_unlock(void)
  * structure.  This should be passed to call_usermodehelper_exec to
  * exec the process and free the structure.
  */
+static
 struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
 						  char **envp, gfp_t gfp_mask)
 {
@@ -494,7 +511,6 @@ struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
   out:
 	return sub_info;
 }
-EXPORT_SYMBOL(call_usermodehelper_setup);
 
 /**
  * call_usermodehelper_setfns - set a cleanup/init function
@@ -512,6 +528,7 @@ EXPORT_SYMBOL(call_usermodehelper_setup);
  * Function must be runnable in either a process context or the
  * context in which call_usermodehelper_exec is called.
  */
+static
 void call_usermodehelper_setfns(struct subprocess_info *info,
 		    int (*init)(struct subprocess_info *info, struct cred *new),
 		    void (*cleanup)(struct subprocess_info *info),
@@ -521,7 +538,6 @@ void call_usermodehelper_setfns(struct subprocess_info *info,
 	info->init = init;
 	info->data = data;
 }
-EXPORT_SYMBOL(call_usermodehelper_setfns);
 
 /**
  * call_usermodehelper_exec - start a usermode application
@@ -535,6 +551,7 @@ EXPORT_SYMBOL(call_usermodehelper_setfns);
  * asynchronously if wait is not set, and runs as a child of keventd.
  * (ie. it runs with full root capabilities).
  */
+static
 int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
@@ -548,6 +565,16 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 		retval = -EBUSY;
 		goto out;
 	}
+	/*
+	 * Worker thread must not wait for khelper thread at below
+	 * wait_for_completion() if the thread was created with CLONE_VFORK
+	 * flag, for khelper thread is already waiting for the thread at
+	 * wait_for_completion() in do_fork().
+	 */
+	if (wait != UMH_NO_WAIT && current == kmod_thread_locker) {
+		retval = -EBUSY;
+		goto out;
+	}
 
 	sub_info->complete = &done;
 	sub_info->wait = wait;
@@ -576,7 +603,31 @@ unlock:
 	helper_unlock();
 	return retval;
 }
-EXPORT_SYMBOL(call_usermodehelper_exec);
+
+/*
+ * call_usermodehelper_fns() will not run the caller-provided cleanup function
+ * if a memory allocation failure is experienced.  So the caller might need to
+ * check the call_usermodehelper_fns() return value: if it is -ENOMEM, perform
+ * the necessaary cleanup within the caller.
+ */
+int call_usermodehelper_fns(
+	char *path, char **argv, char **envp, int wait,
+	int (*init)(struct subprocess_info *info, struct cred *new),
+	void (*cleanup)(struct subprocess_info *), void *data)
+{
+	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);
+
+	if (info == NULL)
+		return -ENOMEM;
+
+	call_usermodehelper_setfns(info, init, cleanup, data);
+
+	return call_usermodehelper_exec(info, wait);
+}
+EXPORT_SYMBOL(call_usermodehelper_fns);
 
 static int proc_cap_handler(struct ctl_table *table, int write,
 			 void __user *buffer, size_t *lenp, loff_t *ppos)