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once: Fix panic when module unload 

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>
This commit is contained in:
Kefeng Wang 2021-08-06 16:21:24 +08:00 committed by David S. Miller
parent d329e41a08
commit 1027b96ec9
2 changed files with 10 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/once.h
View File

@ -7,7 +7,7 @@
bool __do_once_start(bool *done, unsigned long *flags);
void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags);
unsigned long *flags, 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
@ -46,7 +46,7 @@ void __do_once_done(bool *done, struct static_key_true *once_key,
if (unlikely(___ret)) { \
func(__VA_ARGS__); \
__do_once_done(&___done, &___once_key, \
&___flags); \
&___flags, THIS_MODULE); \
} \
} \
___ret; \

11
lib/once.c
View File

@ -3,10 +3,12 @@
#include <linux/spinlock.h>
#include <linux/once.h>
#include <linux/random.h>
#include <linux/module.h>
struct once_work {
struct work_struct work;
struct static_key_true *key;
struct module *module;
};
static void once_deferred(struct work_struct *w)
@ -16,10 +18,11 @@ static void once_deferred(struct work_struct *w)
work = container_of(w, struct once_work, work);
BUG_ON(!static_key_enabled(work->key));
static_branch_disable(work->key);
module_put(work->module);
kfree(work);
}
static void once_disable_jump(struct static_key_true *key)
static void once_disable_jump(struct static_key_true *key, struct module *mod)
{
struct once_work *w;
@ -29,6 +32,8 @@ static void once_disable_jump(struct static_key_true *key)
INIT_WORK(&w->work, once_deferred);
w->key = key;
w->module = mod;
__module_get(mod);
schedule_work(&w->work);
}
@ -53,11 +58,11 @@ bool __do_once_start(bool *done, unsigned long *flags)
EXPORT_SYMBOL(__do_once_start);
void __do_once_done(bool *done, struct static_key_true *once_key,
unsigned long *flags)
unsigned long *flags, struct module *mod)
__releases(once_lock)
{
*done = true;
spin_unlock_irqrestore(&once_lock, *flags);
once_disable_jump(once_key);
once_disable_jump(once_key, mod);
}
EXPORT_SYMBOL(__do_once_done);