From: Masami Hiramatsu mhiramat@kernel.org
[ Upstream commit bf08949cc8b98b7d1e20cfbba169a5938d42dae8 ]
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_mutex) to the list_for_each_entry_rcu() to suppress this warning, This also fixes similar issue in mod_find() and each_symbol_section().
Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Jessica Yu jeyu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/module.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/kernel/module.c b/kernel/module.c index 9fb8fa22e16b3..135861c2ac782 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))