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1027b96ec9
DO_ONCE
DEFINE_STATIC_KEY_TRUE(___once_key);
__do_once_done
once_disable_jump(once_key);
INIT_WORK(&w->work, once_deferred);
struct once_work *w;
w->key = key;
schedule_work(&w->work); module unload
//*the key is
destroy*
process_one_work
once_deferred
BUG_ON(!static_key_enabled(work->key));
static_key_count((struct static_key *)x) //*access key, crash*
When module uses DO_ONCE mechanism, it could crash due to the above
concurrency problem, we could reproduce it with link[1].
Fix it by add/put module refcount in the once work process.
[1] https://lore.kernel.org/netdev/eaa6c371-465e-57eb-6be9-f4b16b9d7cbf@huawei.com/
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Eric Dumazet <edumazet@google.com>
Reported-by: Minmin chen <chenmingmin@huawei.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
60 lines
1.9 KiB
C
60 lines
1.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_ONCE_H
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#define _LINUX_ONCE_H
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#include <linux/types.h>
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#include <linux/jump_label.h>
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bool __do_once_start(bool *done, unsigned long *flags);
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void __do_once_done(bool *done, struct static_key_true *once_key,
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unsigned long *flags, struct module *mod);
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/* Call a function exactly once. The idea of DO_ONCE() is to perform
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* a function call such as initialization of random seeds, etc, only
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* once, where DO_ONCE() can live in the fast-path. After @func has
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* been called with the passed arguments, the static key will patch
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* out the condition into a nop. DO_ONCE() guarantees type safety of
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* arguments!
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*
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* Not that the following is not equivalent ...
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*
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* DO_ONCE(func, arg);
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* DO_ONCE(func, arg);
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*
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* ... to this version:
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*
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* void foo(void)
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* {
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* DO_ONCE(func, arg);
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* }
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*
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* foo();
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* foo();
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*
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* In case the one-time invocation could be triggered from multiple
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* places, then a common helper function must be defined, so that only
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* a single static key will be placed there!
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*/
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#define DO_ONCE(func, ...) \
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({ \
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bool ___ret = false; \
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static bool ___done = false; \
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static DEFINE_STATIC_KEY_TRUE(___once_key); \
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if (static_branch_unlikely(&___once_key)) { \
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unsigned long ___flags; \
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___ret = __do_once_start(&___done, &___flags); \
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if (unlikely(___ret)) { \
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func(__VA_ARGS__); \
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__do_once_done(&___done, &___once_key, \
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&___flags, THIS_MODULE); \
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} \
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} \
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___ret; \
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})
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#define get_random_once(buf, nbytes) \
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DO_ONCE(get_random_bytes, (buf), (nbytes))
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#define get_random_once_wait(buf, nbytes) \
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DO_ONCE(get_random_bytes_wait, (buf), (nbytes)) \
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#endif /* _LINUX_ONCE_H */
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