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author | Peter Zijlstra <peterz@infradead.org> | 2015-05-27 01:39:35 (GMT) |
---|---|---|
committer | Rusty Russell <rusty@rustcorp.com.au> | 2015-05-28 02:01:52 (GMT) |
commit | 0be964be0d45084245673c971d72a4b51690231d (patch) | |
tree | c3d0f0497d325c28f344adda9c3305e75e550c60 | |
parent | bed831f9a251968272dae10a83b512c7db256ef0 (diff) | |
download | linux-0be964be0d45084245673c971d72a4b51690231d.tar.xz |
module: Sanitize RCU usage and locking
Currently the RCU usage in module is an inconsistent mess of RCU and
RCU-sched, this is broken for CONFIG_PREEMPT where synchronize_rcu()
does not imply synchronize_sched().
Most usage sites use preempt_{dis,en}able() which is RCU-sched, but
(most of) the modification sites use synchronize_rcu(). With the
exception of the module bug list, which actually uses RCU.
Convert everything over to RCU-sched.
Furthermore add lockdep asserts to all sites, because it's not at all
clear to me the required locking is observed, esp. on exported
functions.
Cc: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r-- | include/linux/module.h | 12 | ||||
-rw-r--r-- | kernel/module.c | 40 | ||||
-rw-r--r-- | lib/bug.c | 7 |
3 files changed, 47 insertions, 12 deletions
diff --git a/include/linux/module.h b/include/linux/module.h index c883b86..fb56dd8 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -421,14 +421,22 @@ struct symsearch { bool unused; }; -/* Search for an exported symbol by name. */ +/* + * Search for an exported symbol by name. + * + * Must be called with module_mutex held or preemption disabled. + */ const struct kernel_symbol *find_symbol(const char *name, struct module **owner, const unsigned long **crc, bool gplok, bool warn); -/* Walk the exported symbol table */ +/* + * Walk the exported symbol table + * + * Must be called with module_mutex held or preemption disabled. + */ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, struct module *owner, void *data), void *data); diff --git a/kernel/module.c b/kernel/module.c index 1150d52..a15899e 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -105,6 +105,22 @@ static LIST_HEAD(modules); struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */ #endif /* CONFIG_KGDB_KDB */ +static void module_assert_mutex(void) +{ + lockdep_assert_held(&module_mutex); +} + +static void module_assert_mutex_or_preempt(void) +{ +#ifdef CONFIG_LOCKDEP + if (unlikely(!debug_locks)) + return; + + WARN_ON(!rcu_read_lock_sched_held() && + !lockdep_is_held(&module_mutex)); +#endif +} + #ifdef CONFIG_MODULE_SIG #ifdef CONFIG_MODULE_SIG_FORCE static bool sig_enforce = true; @@ -318,6 +334,8 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, #endif }; + module_assert_mutex_or_preempt(); + if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data)) return true; @@ -457,6 +475,8 @@ static struct module *find_module_all(const char *name, size_t len, { struct module *mod; + module_assert_mutex(); + list_for_each_entry(mod, &modules, list) { if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) continue; @@ -1860,8 +1880,8 @@ static void free_module(struct module *mod) list_del_rcu(&mod->list); /* Remove this module from bug list, this uses list_del_rcu */ module_bug_cleanup(mod); - /* Wait for RCU synchronizing before releasing mod->list and buglist. */ - synchronize_rcu(); + /* Wait for RCU-sched synchronizing before releasing mod->list and buglist. */ + synchronize_sched(); mutex_unlock(&module_mutex); /* This may be NULL, but that's OK */ @@ -3133,11 +3153,11 @@ static noinline int do_init_module(struct module *mod) mod->init_text_size = 0; /* * We want to free module_init, but be aware that kallsyms may be - * walking this with preempt disabled. In all the failure paths, - * we call synchronize_rcu/synchronize_sched, but we don't want - * to slow down the success path, so use actual RCU here. + * walking this with preempt disabled. In all the failure paths, we + * call synchronize_sched(), but we don't want to slow down the success + * path, so use actual RCU here. */ - call_rcu(&freeinit->rcu, do_free_init); + call_rcu_sched(&freeinit->rcu, do_free_init); mutex_unlock(&module_mutex); wake_up_all(&module_wq); @@ -3395,8 +3415,8 @@ static int load_module(struct load_info *info, const char __user *uargs, /* Unlink carefully: kallsyms could be walking list. */ list_del_rcu(&mod->list); wake_up_all(&module_wq); - /* Wait for RCU synchronizing before releasing mod->list. */ - synchronize_rcu(); + /* Wait for RCU-sched synchronizing before releasing mod->list. */ + synchronize_sched(); mutex_unlock(&module_mutex); free_module: /* Free lock-classes; relies on the preceding sync_rcu() */ @@ -3663,6 +3683,8 @@ int module_kallsyms_on_each_symbol(int (*fn)(void *, const char *, unsigned int i; int ret; + module_assert_mutex(); + list_for_each_entry(mod, &modules, list) { if (mod->state == MODULE_STATE_UNFORMED) continue; @@ -3837,6 +3859,8 @@ struct module *__module_address(unsigned long addr) if (addr < module_addr_min || addr > module_addr_max) return NULL; + module_assert_mutex_or_preempt(); + list_for_each_entry_rcu(mod, &modules, list) { if (mod->state == MODULE_STATE_UNFORMED) continue; @@ -66,7 +66,7 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr) struct module *mod; const struct bug_entry *bug = NULL; - rcu_read_lock(); + rcu_read_lock_sched(); list_for_each_entry_rcu(mod, &module_bug_list, bug_list) { unsigned i; @@ -77,7 +77,7 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr) } bug = NULL; out: - rcu_read_unlock(); + rcu_read_unlock_sched(); return bug; } @@ -88,6 +88,8 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, char *secstrings; unsigned int i; + lockdep_assert_held(&module_mutex); + mod->bug_table = NULL; mod->num_bugs = 0; @@ -113,6 +115,7 @@ void module_bug_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, void module_bug_cleanup(struct module *mod) { + lockdep_assert_held(&module_mutex); list_del_rcu(&mod->bug_list); } |