247bc03742
There is a race condition between the freezer and request_firmware() such that if request_firmware() is run on one CPU and freeze_processes() is run on another CPU and usermodehelper_disable() called by it succeeds to grab umhelper_sem for writing before usermodehelper_read_trylock() called from request_firmware() acquires it for reading, the request_firmware() will fail and trigger a WARN_ON() complaining that it was called at a wrong time. However, in fact, it wasn't called at a wrong time and freeze_processes() simply happened to be executed simultaneously. To avoid this race, at least in some cases, modify usermodehelper_read_trylock() so that it doesn't fail if the freezing of tasks has just started and hasn't been completed yet. Instead, during the freezing of tasks, it will try to freeze the task that has called it so that it can wait until user space is thawed without triggering the scary warning. For this purpose, change usermodehelper_disabled so that it can take three different values, UMH_ENABLED (0), UMH_FREEZING and UMH_DISABLED. The first one means that usermode helpers are enabled, the last one means "hard disable" (i.e. the system is not ready for usermode helpers to be used) and the second one is reserved for the freezer. Namely, when freeze_processes() is started, it sets usermodehelper_disabled to UMH_FREEZING which tells usermodehelper_read_trylock() that it shouldn't fail just yet and should call try_to_freeze() if woken up and cannot return immediately. This way all freezable tasks that happen to call request_firmware() right before freeze_processes() is started and lose the race for umhelper_sem with it will be frozen and will sleep until thaw_processes() unsets usermodehelper_disabled. [For the non-freezable callers of request_firmware() the race for umhelper_sem against freeze_processes() is unfortunately unavoidable.] Reported-by: Stephen Boyd <sboyd@codeaurora.org> Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: stable@vger.kernel.org
139 lines
4.2 KiB
C
139 lines
4.2 KiB
C
#ifndef __LINUX_KMOD_H__
|
|
#define __LINUX_KMOD_H__
|
|
|
|
/*
|
|
* include/linux/kmod.h
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program; if not, write to the Free Software
|
|
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
*/
|
|
|
|
#include <linux/gfp.h>
|
|
#include <linux/stddef.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/compiler.h>
|
|
#include <linux/workqueue.h>
|
|
#include <linux/sysctl.h>
|
|
|
|
#define KMOD_PATH_LEN 256
|
|
|
|
#ifdef CONFIG_MODULES
|
|
extern char modprobe_path[]; /* for sysctl */
|
|
/* modprobe exit status on success, -ve on error. Return value
|
|
* usually useless though. */
|
|
extern __printf(2, 3)
|
|
int __request_module(bool wait, const char *name, ...);
|
|
#define request_module(mod...) __request_module(true, mod)
|
|
#define request_module_nowait(mod...) __request_module(false, mod)
|
|
#define try_then_request_module(x, mod...) \
|
|
((x) ?: (__request_module(true, mod), (x)))
|
|
#else
|
|
static inline int request_module(const char *name, ...) { return -ENOSYS; }
|
|
static inline int request_module_nowait(const char *name, ...) { return -ENOSYS; }
|
|
#define try_then_request_module(x, mod...) (x)
|
|
#endif
|
|
|
|
|
|
struct cred;
|
|
struct file;
|
|
|
|
#define UMH_NO_WAIT 0 /* don't wait at all */
|
|
#define UMH_WAIT_EXEC 1 /* wait for the exec, but not the process */
|
|
#define UMH_WAIT_PROC 2 /* wait for the process to complete */
|
|
#define UMH_KILLABLE 4 /* wait for EXEC/PROC killable */
|
|
|
|
struct subprocess_info {
|
|
struct work_struct work;
|
|
struct completion *complete;
|
|
char *path;
|
|
char **argv;
|
|
char **envp;
|
|
int wait;
|
|
int retval;
|
|
int (*init)(struct subprocess_info *info, struct cred *new);
|
|
void (*cleanup)(struct subprocess_info *info);
|
|
void *data;
|
|
};
|
|
|
|
/* Allocate a subprocess_info structure */
|
|
struct subprocess_info *call_usermodehelper_setup(char *path, char **argv,
|
|
char **envp, gfp_t gfp_mask);
|
|
|
|
/* Set various pieces of state into the subprocess_info structure */
|
|
void call_usermodehelper_setfns(struct subprocess_info *info,
|
|
int (*init)(struct subprocess_info *info, struct cred *new),
|
|
void (*cleanup)(struct subprocess_info *info),
|
|
void *data);
|
|
|
|
/* Actually execute the sub-process */
|
|
int call_usermodehelper_exec(struct subprocess_info *info, int wait);
|
|
|
|
/* Free the subprocess_info. This is only needed if you're not going
|
|
to call call_usermodehelper_exec */
|
|
void call_usermodehelper_freeinfo(struct subprocess_info *info);
|
|
|
|
static inline 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);
|
|
}
|
|
|
|
static inline int
|
|
call_usermodehelper(char *path, char **argv, char **envp, int wait)
|
|
{
|
|
return call_usermodehelper_fns(path, argv, envp, wait,
|
|
NULL, NULL, NULL);
|
|
}
|
|
|
|
extern struct ctl_table usermodehelper_table[];
|
|
|
|
enum umh_disable_depth {
|
|
UMH_ENABLED = 0,
|
|
UMH_FREEZING,
|
|
UMH_DISABLED,
|
|
};
|
|
|
|
extern void usermodehelper_init(void);
|
|
|
|
extern int __usermodehelper_disable(enum umh_disable_depth depth);
|
|
extern void __usermodehelper_set_disable_depth(enum umh_disable_depth depth);
|
|
|
|
static inline int usermodehelper_disable(void)
|
|
{
|
|
return __usermodehelper_disable(UMH_DISABLED);
|
|
}
|
|
|
|
static inline void usermodehelper_enable(void)
|
|
{
|
|
__usermodehelper_set_disable_depth(UMH_ENABLED);
|
|
}
|
|
|
|
extern int usermodehelper_read_trylock(void);
|
|
extern long usermodehelper_read_lock_wait(long timeout);
|
|
extern void usermodehelper_read_unlock(void);
|
|
|
|
#endif /* __LINUX_KMOD_H__ */
|