Merge branch 'x86/platform' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into stable/for-linus-3.7

* 'x86/platform' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (9690 commits)
  x86: Document x86_init.paging.pagetable_init()
  x86: xen: Cleanup and remove x86_init.paging.pagetable_setup_done()
  x86: Move paging_init() call to x86_init.paging.pagetable_init()
  x86: Rename pagetable_setup_start() to pagetable_init()
  x86: Remove base argument from x86_init.paging.pagetable_setup_start
  Linux 3.6-rc5
  HID: tpkbd: work even if the new Lenovo Keyboard driver is not configured
  Remove user-triggerable BUG from mpol_to_str
  xen/pciback: Fix proper FLR steps.
  uml: fix compile error in deliver_alarm()
  dj: memory scribble in logi_dj
  Fix order of arguments to compat_put_time[spec|val]
  xen: Use correct masking in xen_swiotlb_alloc_coherent.
  xen: fix logical error in tlb flushing
  xen/p2m: Fix one-off error in checking the P2M tree directory.
  powerpc: Don't use __put_user() in patch_instruction
  powerpc: Make sure IPI handlers see data written by IPI senders
  powerpc: Restore correct DSCR in context switch
  powerpc: Fix DSCR inheritance in copy_thread()
  powerpc: Keep thread.dscr and thread.dscr_inherit in sync
  ...

1 files changed, 35 insertions, 2 deletions

diff --git a/kernel/kmod.c b/kernel/kmod.c
index ff2c7cb86d7..6f99aead66c 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
 
@@ -221,6 +228,13 @@ fail:
 	return 0;
 }
 
+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)
@@ -295,9 +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:
@@ -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;
@@ -577,6 +604,12 @@ unlock:
 	return retval;
 }
 
+/*
+ * 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),