Messages in this thread | | | Date | Sat, 02 Oct 2010 18:00:34 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH 2/5] jump label: Fix deadlock b/w jump_label_mutex vs. text_mutex |
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(2010/10/02 6:23), Jason Baron wrote: > register_kprobe() downs the 'text_mutex' and then calls > jump_label_text_reserved(), which downs the 'jump_label_mutex'. > However, the jump label code takes those mutexes in the reverse > order. > > Fix by requiring the caller of jump_label_text_reserved() to do > the jump label locking via the newly added: jump_label_lock(), > jump_label_unlock(). Currently, kprobes is the only user > of jump_label_text_reserved(). >
Looks good for me;)
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Thank you,
> > Signed-off-by: Jason Baron <jbaron@redhat.com> > Reported-by: Ingo Molnar <mingo@elte.hu> > --- > include/linux/jump_label.h | 5 +++++ > kernel/jump_label.c | 33 +++++++++++++++++++++------------ > kernel/kprobes.c | 6 ++++++ > 3 files changed, 32 insertions(+), 12 deletions(-) > > diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h > index b72cd9f..cf213d1 100644 > --- a/include/linux/jump_label.h > +++ b/include/linux/jump_label.h > @@ -18,6 +18,8 @@ struct module; > extern struct jump_entry __start___jump_table[]; > extern struct jump_entry __stop___jump_table[]; > > +extern void jump_label_lock(void); > +extern void jump_label_unlock(void); > extern void arch_jump_label_transform(struct jump_entry *entry, > enum jump_label_type type); > extern void arch_jump_label_text_poke_early(jump_label_t addr); > @@ -59,6 +61,9 @@ static inline int jump_label_text_reserved(void *start, void *end) > return 0; > } > > +static inline void jump_label_lock(void) {} > +static inline void jump_label_unlock(void) {} > + > #endif > > #endif > diff --git a/kernel/jump_label.c b/kernel/jump_label.c > index e2fad92..2add1a7 100644 > --- a/kernel/jump_label.c > +++ b/kernel/jump_label.c > @@ -39,6 +39,16 @@ struct jump_label_module_entry { > struct module *mod; > }; > > +void jump_label_lock(void) > +{ > + mutex_lock(&jump_label_mutex); > +} > + > +void jump_label_unlock(void) > +{ > + mutex_unlock(&jump_label_mutex); > +} > + > static int jump_label_cmp(const void *a, const void *b) > { > const struct jump_entry *jea = a; > @@ -152,7 +162,7 @@ void jump_label_update(unsigned long key, enum jump_label_type type) > struct jump_label_module_entry *e_module; > int count; > > - mutex_lock(&jump_label_mutex); > + jump_label_lock(); > entry = get_jump_label_entry((jump_label_t)key); > if (entry) { > count = entry->nr_entries; > @@ -175,7 +185,7 @@ void jump_label_update(unsigned long key, enum jump_label_type type) > } > } > } > - mutex_unlock(&jump_label_mutex); > + jump_label_unlock(); > } > > static int addr_conflict(struct jump_entry *entry, void *start, void *end) > @@ -232,6 +242,7 @@ out: > * overlaps with any of the jump label patch addresses. Code > * that wants to modify kernel text should first verify that > * it does not overlap with any of the jump label addresses. > + * Caller must hold jump_label_mutex. > * > * returns 1 if there is an overlap, 0 otherwise > */ > @@ -242,7 +253,6 @@ int jump_label_text_reserved(void *start, void *end) > struct jump_entry *iter_stop = __start___jump_table; > int conflict = 0; > > - mutex_lock(&jump_label_mutex); > iter = iter_start; > while (iter < iter_stop) { > if (addr_conflict(iter, start, end)) { > @@ -257,7 +267,6 @@ int jump_label_text_reserved(void *start, void *end) > conflict = module_conflict(start, end); > #endif > out: > - mutex_unlock(&jump_label_mutex); > return conflict; > } > > @@ -268,7 +277,7 @@ static __init int init_jump_label(void) > struct jump_entry *iter_stop = __stop___jump_table; > struct jump_entry *iter; > > - mutex_lock(&jump_label_mutex); > + jump_label_lock(); > ret = build_jump_label_hashtable(__start___jump_table, > __stop___jump_table); > iter = iter_start; > @@ -276,7 +285,7 @@ static __init int init_jump_label(void) > arch_jump_label_text_poke_early(iter->code); > iter++; > } > - mutex_unlock(&jump_label_mutex); > + jump_label_unlock(); > return ret; > } > early_initcall(init_jump_label); > @@ -409,21 +418,21 @@ jump_label_module_notify(struct notifier_block *self, unsigned long val, > > switch (val) { > case MODULE_STATE_COMING: > - mutex_lock(&jump_label_mutex); > + jump_label_lock(); > ret = add_jump_label_module(mod); > if (ret) > remove_jump_label_module(mod); > - mutex_unlock(&jump_label_mutex); > + jump_label_unlock(); > break; > case MODULE_STATE_GOING: > - mutex_lock(&jump_label_mutex); > + jump_label_lock(); > remove_jump_label_module(mod); > - mutex_unlock(&jump_label_mutex); > + jump_label_unlock(); > break; > case MODULE_STATE_LIVE: > - mutex_lock(&jump_label_mutex); > + jump_label_lock(); > remove_module_init(mod); > - mutex_unlock(&jump_label_mutex); > + jump_label_unlock(); > break; > } > return ret; > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index ec4210c..d45d72e 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -1145,13 +1145,16 @@ int __kprobes register_kprobe(struct kprobe *p) > return ret; > > preempt_disable(); > + jump_label_lock(); > if (!kernel_text_address((unsigned long) p->addr) || > in_kprobes_functions((unsigned long) p->addr) || > ftrace_text_reserved(p->addr, p->addr) || > jump_label_text_reserved(p->addr, p->addr)) { > preempt_enable(); > + jump_label_unlock(); > return -EINVAL; > } > + jump_label_unlock(); > > /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */ > p->flags &= KPROBE_FLAG_DISABLED; > @@ -1186,6 +1189,8 @@ int __kprobes register_kprobe(struct kprobe *p) > INIT_LIST_HEAD(&p->list); > mutex_lock(&kprobe_mutex); > > + jump_label_lock(); /* needed to call jump_label_text_reserved() */ > + > get_online_cpus(); /* For avoiding text_mutex deadlock. */ > mutex_lock(&text_mutex); > > @@ -1213,6 +1218,7 @@ int __kprobes register_kprobe(struct kprobe *p) > out: > mutex_unlock(&text_mutex); > put_online_cpus(); > + jump_label_unlock(); > mutex_unlock(&kprobe_mutex); > > if (probed_mod)
-- Masami HIRAMATSU 2nd Dept. Linux Technology Center Hitachi, Ltd., Systems Development Laboratory E-mail: masami.hiramatsu.pt@hitachi.com
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