+ sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     sysctl: use RCU protected sysctl for ocfs group add helper
has been added to the -mm tree.  Its filename is
     sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper.patch

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------------------------------------------------------
Subject: sysctl: use RCU protected sysctl for ocfs group add helper
From: Andi Kleen <andi@firstfloor.org>

This avoids races with unlocked sysctl()

Also saves ~220 bytes in the data segment.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>
Cc: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Joel Becker <Joel.Becker@oracle.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/ocfs2/stackglue.c |   17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff -puN fs/ocfs2/stackglue.c~sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper fs/ocfs2/stackglue.c
--- a/fs/ocfs2/stackglue.c~sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper
+++ a/fs/ocfs2/stackglue.c
@@ -27,6 +27,7 @@
 #include <linux/kobject.h>
 #include <linux/sysfs.h>
 #include <linux/sysctl.h>
+#include <linux/rcustring.h>
 
 #include "ocfs2_fs.h"
 
@@ -40,7 +41,7 @@ static struct ocfs2_locking_protocol *lp
 static DEFINE_SPINLOCK(ocfs2_stack_lock);
 static LIST_HEAD(ocfs2_stack_list);
 static char cluster_stack_name[OCFS2_STACK_LABEL_LEN + 1];
-static char ocfs2_hb_ctl_path[OCFS2_MAX_HB_CTL_PATH] = "/sbin/ocfs2_hb_ctl";
+static char *ocfs2_hb_ctl_path = "/sbin/ocfs2_hb_ctl";
 
 /*
  * The stack currently in use.  If not null, active_stack->sp_count > 0,
@@ -395,8 +396,15 @@ static void ocfs2_leave_group(const char
 {
 	int ret;
 	char *argv[5], *envp[3];
+	char *helper;
 
-	argv[0] = ocfs2_hb_ctl_path;
+	helper = access_rcu_string(&ocfs2_hb_ctl_path, OCFS2_MAX_HB_CTL_PATH, GFP_KERNEL);
+	if (!helper) {
+		printk(KERN_ERR "ocfs2_leave_group: no memory\n");
+		return;
+	}
+
+	argv[0] = helper;
 	argv[1] = "-K";
 	argv[2] = "-u";
 	argv[3] = (char *)group;
@@ -414,6 +422,7 @@ static void ocfs2_leave_group(const char
 		       "\"%s %s %s %s\"\n",
 		       ret, argv[0], argv[1], argv[2], argv[3]);
 	}
+	kfree(helper);
 }
 
 /*
@@ -621,10 +630,10 @@ error:
 static ctl_table ocfs2_nm_table[] = {
 	{
 		.procname	= "hb_ctl_path",
-		.data		= ocfs2_hb_ctl_path,
+		.data		= &ocfs2_hb_ctl_path,
 		.maxlen		= OCFS2_MAX_HB_CTL_PATH,
 		.mode		= 0644,
-		.proc_handler	= proc_dostring,
+		.proc_handler	= proc_rcu_string,
 	},
 	{ }
 };
_

Patches currently in -mm which might be from andi@firstfloor.org are

kernel-signalc-fix-kernel-information-leak-with-print-fatal-signals=1.patch
proc-revert-procfs-provide-stack-information-for-threads.patch
kfifo-use-void-pointers-for-user-buffers.patch
kfifo-sanitize-_user-error-handling.patch
kfifo-add-kfifo_out_peek.patch
kfifo-add-kfifo_initialized.patch
kfifo-document-everywhere-that-size-has-to-be-power-of-two.patch
hardware-latency-detector-remove-default-m.patch
kbuild-move-fno-dwarf2-cfi-asm-to-powerpc-only.patch
mm-introduce-dump_page-and-print-symbolic-flag-names.patch
coredump-unify-dump_seek-implementations-for-each-binfmt_c.patch
coredump-move-dump_write-and-dump_seek-into-a-header-file.patch
elf-coredump-replace-elf_core_extra_-macros-by-functions.patch
elf-coredump-make-offset-calculation-process-and-writing-process-explicit.patch
elf-coredump-add-extended-numbering-support.patch
tracehooks-kill-some-pt_ptraced-checks.patch
tracehooks-check-pt_ptraced-before-reporting-the-single-step.patch
ptrace_signal-check-pt_ptraced-before-reporting-a-signal.patch
export-__ptrace_detach-and-do_notify_parent_cldstop.patch
reorder-the-code-in-kernel-ptracec.patch
implement-utrace-ptrace.patch
utrace-core.patch
rcu-add-rcustring-adt-for-rcu-protected-strings.patch
add-a-kernel_address-that-works-for-data-too.patch
sysctl-add-proc_rcu_string-to-manage-sysctls-using-rcu-strings.patch
sysctl-use-rcu-strings-for-core_pattern-sysctl.patch
sysctl-add-call_usermodehelper_cleanup.patch
sysctl-convert-modprobe_path-to-proc_rcu_string.patch
sysctl-convert-poweroff_command-to-proc_rcu_string.patch
sysctl-convert-hotplug-helper-string-to-proc_rcu_string.patch
sysctl-use-rcu-protected-sysctl-for-ocfs-group-add-helper.patch