Messages in this thread | | | Date | Fri, 6 Dec 2019 10:21:29 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH] modules: lockdep: Suppress suspicious RCU usage warning |
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On Thu, 5 Dec 2019 20:17:59 +0100 Jessica Yu <jeyu@kernel.org> wrote:
> +++ Masami Hiramatsu [03/12/19 15:14 +0900]: > >While running kprobe module test, find_module_all() caused > >a suspicious RCU usage warning. > > > >----- > > ============================= > > WARNING: suspicious RCU usage > > 5.4.0-next-20191202+ #63 Not tainted > > ----------------------------- > > kernel/module.c:619 RCU-list traversed in non-reader section!! > > > > other info that might help us debug this: > > > > > > rcu_scheduler_active = 2, debug_locks = 1 > > 1 lock held by rmmod/642: > > #0: ffffffff8227da80 (module_mutex){+.+.}, at: __x64_sys_delete_module+0x9a/0x230 > > > > stack backtrace: > > CPU: 0 PID: 642 Comm: rmmod Not tainted 5.4.0-next-20191202+ #63 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 > > Call Trace: > > dump_stack+0x71/0xa0 > > find_module_all+0xc1/0xd0 > > __x64_sys_delete_module+0xac/0x230 > > ? do_syscall_64+0x12/0x1f0 > > do_syscall_64+0x50/0x1f0 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x4b6d49 > >----- > > > >This is because list_for_each_entry_rcu(modules) is called > >without rcu_read_lock(). This is safe because the module_mutex > >is locked. > > > >Pass lockdep_is_held(&module_lock) to the list_for_each_entry_rcu() > > s/module_lock/module_mutex/, but you don't have to respin the patch > just for this.
Oops.
> > >to suppress this warning, This also fixes similar issue in > >mod_find() and each_symbol_section(). > > > >Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> > > Thanks Masami! This looks good. I'll queue this up shortly after the > merge window.
Thank you for merging :)
> > Jessica > > >--- > > kernel/module.c | 9 ++++++--- > > 1 file changed, 6 insertions(+), 3 deletions(-) > > > >diff --git a/kernel/module.c b/kernel/module.c > >index cb6250be6ee9..38e5c6a7451b 100644 > >--- a/kernel/module.c > >+++ b/kernel/module.c > >@@ -214,7 +214,8 @@ static struct module *mod_find(unsigned long addr) > > { > > struct module *mod; > > > >- list_for_each_entry_rcu(mod, &modules, list) { > >+ list_for_each_entry_rcu(mod, &modules, list, > >+ lockdep_is_held(&module_mutex)) { > > if (within_module(addr, mod)) > > return mod; > > } > >@@ -448,7 +449,8 @@ bool each_symbol_section(bool (*fn)(const struct symsearch *arr, > > if (each_symbol_in_section(arr, ARRAY_SIZE(arr), NULL, fn, data)) > > return true; > > > >- list_for_each_entry_rcu(mod, &modules, list) { > >+ list_for_each_entry_rcu(mod, &modules, list, > >+ lockdep_is_held(&module_mutex)) { > > struct symsearch arr[] = { > > { mod->syms, mod->syms + mod->num_syms, mod->crcs, > > NOT_GPL_ONLY, false }, > >@@ -616,7 +618,8 @@ static struct module *find_module_all(const char *name, size_t len, > > > > module_assert_mutex_or_preempt(); > > > >- list_for_each_entry_rcu(mod, &modules, list) { > >+ list_for_each_entry_rcu(mod, &modules, list, > >+ lockdep_is_held(&module_mutex)) { > > if (!even_unformed && mod->state == MODULE_STATE_UNFORMED) > > continue; > > if (strlen(mod->name) == len && !memcmp(mod->name, name, len)) > >
-- Masami Hiramatsu <mhiramat@kernel.org>
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