From: Andrea Righi andrea.righi@canonical.com
[ Upstream commit f1c6ece23729257fb46562ff9224cf5f61b818da ]
lockdep reports the following deadlock scenario:
WARNING: possible circular locking dependency detected
kworker/1:1/48 is trying to acquire lock: 000000008d7a62b2 (text_mutex){+.+.}, at: kprobe_optimizer+0x163/0x290
but task is already holding lock: 00000000850b5e2d (module_mutex){+.+.}, at: kprobe_optimizer+0x31/0x290
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (module_mutex){+.+.}: __mutex_lock+0xac/0x9f0 mutex_lock_nested+0x1b/0x20 set_all_modules_text_rw+0x22/0x90 ftrace_arch_code_modify_prepare+0x1c/0x20 ftrace_run_update_code+0xe/0x30 ftrace_startup_enable+0x2e/0x50 ftrace_startup+0xa7/0x100 register_ftrace_function+0x27/0x70 arm_kprobe+0xb3/0x130 enable_kprobe+0x83/0xa0 enable_trace_kprobe.part.0+0x2e/0x80 kprobe_register+0x6f/0xc0 perf_trace_event_init+0x16b/0x270 perf_kprobe_init+0xa7/0xe0 perf_kprobe_event_init+0x3e/0x70 perf_try_init_event+0x4a/0x140 perf_event_alloc+0x93a/0xde0 __do_sys_perf_event_open+0x19f/0xf30 __x64_sys_perf_event_open+0x20/0x30 do_syscall_64+0x65/0x1d0 entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (text_mutex){+.+.}: __lock_acquire+0xfcb/0x1b60 lock_acquire+0xca/0x1d0 __mutex_lock+0xac/0x9f0 mutex_lock_nested+0x1b/0x20 kprobe_optimizer+0x163/0x290 process_one_work+0x22b/0x560 worker_thread+0x50/0x3c0 kthread+0x112/0x150 ret_from_fork+0x3a/0x50
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(module_mutex); lock(text_mutex); lock(module_mutex); lock(text_mutex);
*** DEADLOCK ***
As a reproducer I've been using bcc's funccount.py (https://github.com/iovisor/bcc/blob/master/tools/funccount.py), for example:
# ./funccount.py '*interrupt*'
That immediately triggers the lockdep splat.
Fix by acquiring text_mutex before module_mutex in kprobe_optimizer().
Signed-off-by: Andrea Righi andrea.righi@canonical.com Acked-by: Masami Hiramatsu mhiramat@kernel.org Cc: Anil S Keshavamurthy anil.s.keshavamurthy@intel.com Cc: David S. Miller davem@davemloft.net Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Naveen N. Rao naveen.n.rao@linux.ibm.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Fixes: d5b844a2cf50 ("ftrace/x86: Remove possible deadlock between register_kprobe() and ftrace_run_update_code()") Link: http://lkml.kernel.org/r/20190812184302.GA7010@xps-13 Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/kprobes.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 29ff6635d2597..714d63f60460b 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -483,6 +483,7 @@ static DECLARE_DELAYED_WORK(optimizing_work, kprobe_optimizer); */ static void do_optimize_kprobes(void) { + lockdep_assert_held(&text_mutex); /* * The optimization/unoptimization refers online_cpus via * stop_machine() and cpu-hotplug modifies online_cpus. @@ -500,9 +501,7 @@ static void do_optimize_kprobes(void) list_empty(&optimizing_list)) return;
- mutex_lock(&text_mutex); arch_optimize_kprobes(&optimizing_list); - mutex_unlock(&text_mutex); }
/* @@ -513,6 +512,7 @@ static void do_unoptimize_kprobes(void) { struct optimized_kprobe *op, *tmp;
+ lockdep_assert_held(&text_mutex); /* See comment in do_optimize_kprobes() */ lockdep_assert_cpus_held();
@@ -520,7 +520,6 @@ static void do_unoptimize_kprobes(void) if (list_empty(&unoptimizing_list)) return;
- mutex_lock(&text_mutex); arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list); /* Loop free_list for disarming */ list_for_each_entry_safe(op, tmp, &freeing_list, list) { @@ -537,7 +536,6 @@ static void do_unoptimize_kprobes(void) } else list_del_init(&op->list); } - mutex_unlock(&text_mutex); }
/* Reclaim all kprobes on the free_list */ @@ -563,6 +561,7 @@ static void kprobe_optimizer(struct work_struct *work) { mutex_lock(&kprobe_mutex); cpus_read_lock(); + mutex_lock(&text_mutex); /* Lock modules while optimizing kprobes */ mutex_lock(&module_mutex);
@@ -590,6 +589,7 @@ static void kprobe_optimizer(struct work_struct *work) do_free_cleaned_kprobes();
mutex_unlock(&module_mutex); + mutex_unlock(&text_mutex); cpus_read_unlock(); mutex_unlock(&kprobe_mutex);