The patch titled
sysctl: convert modprobe_path to proc_rcu_string()
has been added to the -mm tree. Its filename is
sysctl-convert-modprobe_path-to-proc_rcu_string.patch
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------------------------------------------------------
Subject: sysctl: convert modprobe_path to proc_rcu_string()
From: Andi Kleen <andi@xxxxxxxxxxxxxx>
Avoids races with lockless sysctl
Also saves ~220 bytes in the data segment for default kernels.
Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Cc: Russell King <rmk+lkml@xxxxxxxxxxxxxxxx>
Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/kmod.c | 36 ++++++++++++++++++++++++++++--------
kernel/sysctl.c | 4 ++--
2 files changed, 30 insertions(+), 10 deletions(-)
diff -puN kernel/kmod.c~sysctl-convert-modprobe_path-to-proc_rcu_string kernel/kmod.c
--- a/kernel/kmod.c~sysctl-convert-modprobe_path-to-proc_rcu_string
+++ a/kernel/kmod.c
@@ -35,6 +35,7 @@
#include <linux/resource.h>
#include <linux/notifier.h>
#include <linux/suspend.h>
+#include <linux/rcustring.h>
#include <asm/uaccess.h>
#include <trace/events/module.h>
@@ -48,7 +49,12 @@ static struct workqueue_struct *khelper_
/*
modprobe_path is set via /proc/sys.
*/
-char modprobe_path[KMOD_PATH_LEN] = "/sbin/modprobe";
+char *modprobe_path = "/sbin/modprobe";
+
+static void free_arg(char **argv, char **env)
+{
+ kfree(argv[0]);
+}
/**
* __request_module - try to load a kernel module
@@ -71,7 +77,8 @@ int __request_module(bool wait, const ch
char module_name[MODULE_NAME_LEN];
unsigned int max_modprobes;
int ret;
- char *argv[] = { modprobe_path, "-q", "--", module_name, NULL };
+ char *mp_copy;
+ char *argv[] = { NULL, "-q", "--", module_name, NULL };
static char *envp[] = { "HOME=/",
"TERM=linux",
"PATH=/sbin:/usr/sbin:/bin:/usr/bin",
@@ -80,15 +87,24 @@ int __request_module(bool wait, const ch
#define MAX_KMOD_CONCURRENT 50 /* Completely arbitrary value - KAO */
static int kmod_loop_msg;
+ /* Get a stable-over-sleeps private copy of modprobe_path */
+ mp_copy = access_rcu_string(&modprobe_path, KMOD_PATH_LEN,
+ wait ? GFP_KERNEL : GFP_ATOMIC);
+ if (!mp_copy)
+ return -ENOMEM;
+ argv[0] = mp_copy;
+
va_start(args, fmt);
ret = vsnprintf(module_name, MODULE_NAME_LEN, fmt, args);
va_end(args);
- if (ret >= MODULE_NAME_LEN)
- return -ENAMETOOLONG;
+ if (ret >= MODULE_NAME_LEN) {
+ ret = -ENAMETOOLONG;
+ goto error;
+ }
ret = security_kernel_module_request(module_name);
if (ret)
- return ret;
+ goto error;
/* If modprobe needs a service that is in a module, we get a recursive
* loop. Limit the number of running kmod threads to max_threads/2 or
@@ -111,14 +127,18 @@ int __request_module(bool wait, const ch
"request_module: runaway loop modprobe %s\n",
module_name);
atomic_dec(&kmod_concurrent);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto error;
}
trace_module_request(module_name, wait, _RET_IP_);
- ret = call_usermodehelper(modprobe_path, argv, envp,
- wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC);
+ ret = call_usermodehelper_cleanup(mp_copy, argv, envp,
+ wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC, free_arg);
+ mp_copy = NULL; /* free_arg frees */
atomic_dec(&kmod_concurrent);
+error:
+ kfree(mp_copy);
return ret;
}
EXPORT_SYMBOL(__request_module);
diff -puN kernel/sysctl.c~sysctl-convert-modprobe_path-to-proc_rcu_string kernel/sysctl.c
--- a/kernel/sysctl.c~sysctl-convert-modprobe_path-to-proc_rcu_string
+++ a/kernel/sysctl.c
@@ -121,7 +121,7 @@ static int min_percpu_pagelist_fract = 8
static int ngroups_max = NGROUPS_MAX;
#ifdef CONFIG_MODULES
-extern char modprobe_path[];
+extern char *modprobe_path;
extern int modules_disabled;
#endif
#ifdef CONFIG_CHR_DEV_SG
@@ -532,7 +532,7 @@ static struct ctl_table kern_table[] = {
.data = &modprobe_path,
.maxlen = KMOD_PATH_LEN,
.mode = 0644,
- .proc_handler = proc_dostring,
+ .proc_handler = proc_rcu_string,
},
{
.procname = "modules_disabled",
_
Patches currently in -mm which might be from andi@xxxxxxxxxxxxxx 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
--
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