This is a note to let you know that I've just added the patch titled kprobes: Fix to delay the kprobes jump optimization to the 5.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kprobes-fix-to-delay-the-kprobes-jump-optimization.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From c85c9a2c6e368dc94907e63babb18a9788e5c9b6 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Date: Thu, 18 Feb 2021 23:29:23 +0900 Subject: kprobes: Fix to delay the kprobes jump optimization From: Masami Hiramatsu <mhiramat@xxxxxxxxxx> commit c85c9a2c6e368dc94907e63babb18a9788e5c9b6 upstream. Commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall") moved the kprobe setup in early_initcall(), which includes kprobe jump optimization. The kprobes jump optimizer involves synchronize_rcu_tasks() which depends on the ksoftirqd and rcu_spawn_tasks_*(). However, since those are setup in core_initcall(), kprobes jump optimizer can not run at the early_initcall(). To avoid this issue, make the kprobe optimization disabled in the early_initcall() and enables it in subsys_initcall(). Note that non-optimized kprobes is still available after early_initcall(). Only jump optimization is delayed. Link: https://lkml.kernel.org/r/161365856280.719838.12423085451287256713.stgit@devnote2 Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall") Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: RCU <rcu@xxxxxxxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Daniel Axtens <dja@xxxxxxxxxx> Cc: Frederic Weisbecker <frederic@xxxxxxxxxx> Cc: Neeraj Upadhyay <neeraju@xxxxxxxxxxxxxx> Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: "Theodore Y . Ts'o" <tytso@xxxxxxx> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Reported-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Reported-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Reported-by: Uladzislau Rezki <urezki@xxxxxxxxx> Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/kprobes.c | 31 +++++++++++++++++++++---------- 1 file changed, 21 insertions(+), 10 deletions(-) --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -871,7 +871,6 @@ out: cpus_read_unlock(); } -#ifdef CONFIG_SYSCTL static void optimize_all_kprobes(void) { struct hlist_head *head; @@ -897,6 +896,7 @@ out: mutex_unlock(&kprobe_mutex); } +#ifdef CONFIG_SYSCTL static void unoptimize_all_kprobes(void) { struct hlist_head *head; @@ -2627,18 +2627,14 @@ static int __init init_kprobes(void) } } -#if defined(CONFIG_OPTPROBES) -#if defined(__ARCH_WANT_KPROBES_INSN_SLOT) - /* Init kprobe_optinsn_slots */ - kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE; -#endif - /* By default, kprobes can be optimized */ - kprobes_allow_optimization = true; -#endif - /* By default, kprobes are armed */ kprobes_all_disarmed = false; +#if defined(CONFIG_OPTPROBES) && defined(__ARCH_WANT_KPROBES_INSN_SLOT) + /* Init kprobe_optinsn_slots for allocation */ + kprobe_optinsn_slots.insn_size = MAX_OPTINSN_SIZE; +#endif + err = arch_init_kprobes(); if (!err) err = register_die_notifier(&kprobe_exceptions_nb); @@ -2653,6 +2649,21 @@ static int __init init_kprobes(void) } early_initcall(init_kprobes); +#if defined(CONFIG_OPTPROBES) +static int __init init_optprobes(void) +{ + /* + * Enable kprobe optimization - this kicks the optimizer which + * depends on synchronize_rcu_tasks() and ksoftirqd, that is + * not spawned in early initcall. So delay the optimization. + */ + optimize_all_kprobes(); + + return 0; +} +subsys_initcall(init_optprobes); +#endif + #ifdef CONFIG_DEBUG_FS static void report_probe(struct seq_file *pi, struct kprobe *p, const char *sym, int offset, char *modname, struct kprobe *pp) Patches currently in stable-queue which might be from mhiramat@xxxxxxxxxx are queue-5.10/kprobes-fix-to-delay-the-kprobes-jump-optimization.patch queue-5.10/selftests-ftrace-update-synthetic-event-syntax-error.patch