c8f9b7cd3b
[ Upstream commit edcc8a38b5ac1a3dbd05e113a38a25b937ebefe5 ] The commitc2c60ea37e("once: use __section(".data.once")") moved DO_ONCE's ___done variable to .data.once section, which conflicts with DO_ONCE_LITE() that also uses the same section. This creates a race condition when clear_warn_once is used: Thread 1 (DO_ONCE) Thread 2 (DO_ONCE) __do_once_start read ___done (false) acquire once_lock execute func __do_once_done write ___done (true) __do_once_start release once_lock // Thread 3 clear_warn_once reset ___done read ___done (false) acquire once_lock execute func schedule once_work __do_once_done once_deferred: OK write ___done (true) static_branch_disable release once_lock schedule once_work once_deferred: BUG_ON(!static_key_enabled) DO_ONCE_LITE() in once_lite.h is used by WARN_ON_ONCE() and other warning macros. Keep its ___done flag in the .data..once section and allow resetting by clear_warn_once, as originally intended. In contrast, DO_ONCE() is used for functions like get_random_once() and relies on its ___done flag for internal synchronization. We should not reset DO_ONCE() by clear_warn_once. Fix it by isolating DO_ONCE's ___done into a separate .data..do_once section, shielding it from clear_warn_once. Fixes:c2c60ea37e("once: use __section(".data.once")") Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Qi Xi <xiqi2@huawei.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
#ifndef _LINUX_ONCE_H
|
|
#define _LINUX_ONCE_H
|
|
|
|
#include <linux/types.h>
|
|
#include <linux/jump_label.h>
|
|
|
|
/* Helpers used from arbitrary contexts.
|
|
* Hard irqs are blocked, be cautious.
|
|
*/
|
|
bool __do_once_start(bool *done, unsigned long *flags);
|
|
void __do_once_done(bool *done, struct static_key_true *once_key,
|
|
unsigned long *flags, struct module *mod);
|
|
|
|
/* Variant for process contexts only. */
|
|
bool __do_once_sleepable_start(bool *done);
|
|
void __do_once_sleepable_done(bool *done, struct static_key_true *once_key,
|
|
struct module *mod);
|
|
|
|
/* Call a function exactly once. The idea of DO_ONCE() is to perform
|
|
* a function call such as initialization of random seeds, etc, only
|
|
* once, where DO_ONCE() can live in the fast-path. After @func has
|
|
* been called with the passed arguments, the static key will patch
|
|
* out the condition into a nop. DO_ONCE() guarantees type safety of
|
|
* arguments!
|
|
*
|
|
* Note that the following is not equivalent ...
|
|
*
|
|
* DO_ONCE(func, arg);
|
|
* DO_ONCE(func, arg);
|
|
*
|
|
* ... to this version:
|
|
*
|
|
* void foo(void)
|
|
* {
|
|
* DO_ONCE(func, arg);
|
|
* }
|
|
*
|
|
* foo();
|
|
* foo();
|
|
*
|
|
* In case the one-time invocation could be triggered from multiple
|
|
* places, then a common helper function must be defined, so that only
|
|
* a single static key will be placed there!
|
|
*/
|
|
#define DO_ONCE(func, ...) \
|
|
({ \
|
|
bool ___ret = false; \
|
|
static bool __section(".data..do_once") ___done = false; \
|
|
static DEFINE_STATIC_KEY_TRUE(___once_key); \
|
|
if (static_branch_unlikely(&___once_key)) { \
|
|
unsigned long ___flags; \
|
|
___ret = __do_once_start(&___done, &___flags); \
|
|
if (unlikely(___ret)) { \
|
|
func(__VA_ARGS__); \
|
|
__do_once_done(&___done, &___once_key, \
|
|
&___flags, THIS_MODULE); \
|
|
} \
|
|
} \
|
|
___ret; \
|
|
})
|
|
|
|
/* Variant of DO_ONCE() for process/sleepable contexts. */
|
|
#define DO_ONCE_SLEEPABLE(func, ...) \
|
|
({ \
|
|
bool ___ret = false; \
|
|
static bool __section(".data..do_once") ___done = false; \
|
|
static DEFINE_STATIC_KEY_TRUE(___once_key); \
|
|
if (static_branch_unlikely(&___once_key)) { \
|
|
___ret = __do_once_sleepable_start(&___done); \
|
|
if (unlikely(___ret)) { \
|
|
func(__VA_ARGS__); \
|
|
__do_once_sleepable_done(&___done, &___once_key,\
|
|
THIS_MODULE); \
|
|
} \
|
|
} \
|
|
___ret; \
|
|
})
|
|
|
|
#define get_random_once(buf, nbytes) \
|
|
DO_ONCE(get_random_bytes, (buf), (nbytes))
|
|
|
|
#define get_random_sleepable_once(buf, nbytes) \
|
|
DO_ONCE_SLEEPABLE(get_random_bytes, (buf), (nbytes))
|
|
|
|
#endif /* _LINUX_ONCE_H */
|