From: "Masami Hiramatsu (Google)" mhiramat@kernel.org

commit 4fbd2f83fda0ca44a2ec6421ca3508b355b31858 upstream.

Since forcibly unoptimized kprobes will be put on the freeing_list directly in the unoptimize_kprobe(), do_unoptimize_kprobes() must continue to check the freeing_list even if unoptimizing_list is empty.

This bug can happen if a kprobe is put in an instruction which is in the middle of the jump-replaced instruction sequence of an optprobe, *and* the optprobe is recently unregistered and queued on unoptimizing_list. In this case, the optprobe will be unoptimized forcibly (means immediately) and put it into the freeing_list, expecting the optprobe will be handled in do_unoptimize_kprobe(). But if there is no other optprobes on the unoptimizing_list, current code returns from the do_unoptimize_kprobe() soon and does not handle the optprobe which is on the freeing_list. Then the optprobe will hit the WARN_ON_ONCE() in the do_free_cleaned_kprobes(), because it is not handled in the latter loop of the do_unoptimize_kprobe().

To solve this issue, do not return from do_unoptimize_kprobes() immediately even if unoptimizing_list is empty.

Moreover, this change affects another case. kill_optimized_kprobes() expects kprobe_optimizer() will just free the optprobe on freeing_list. So I changed it to just do list_move() to freeing_list if optprobes are on unoptimizing list. And the do_unoptimize_kprobe() will skip arch_disarm_kprobe() if the probe on freeing_list has gone flag.

Link: https://lore.kernel.org/all/Y8URdIfVr3pq2X8w@xpf.sh.intel.com/ Link: https://lore.kernel.org/all/167448024501.3253718.13037333683110512967.stgit@...

Fixes: e4add247789e ("kprobes: Fix optimize_kprobe()/unoptimize_kprobe() cancellation logic") Reported-by: Pengfei Xu pengfei.xu@intel.com Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org Cc: stable@vger.kernel.org Acked-by: Steven Rostedt (Google) rostedt@goodmis.org [fp: adjust comment conflict regarding commit 223a76b268c9 ("kprobes: Fix coding style issues")] Signed-off-by: Fedor Pchelkin pchelkin@ispras.ru --- kernel/kprobes.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 07d36cee2a80..5d713a7d7e87 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -549,17 +549,15 @@ static void do_unoptimize_kprobes(void) /* See comment in do_optimize_kprobes() */ lockdep_assert_cpus_held();

- /* Unoptimization must be done anytime */ - if (list_empty(&unoptimizing_list)) - return; + if (!list_empty(&unoptimizing_list)) + arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list);

- arch_unoptimize_kprobes(&unoptimizing_list, &freeing_list); - /* Loop free_list for disarming */ + /* Loop on 'freeing_list' for disarming and removing from kprobe hash list */ list_for_each_entry_safe(op, tmp, &freeing_list, list) { /* Switching from detour code to origin */ op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED; - /* Disarm probes if marked disabled */ - if (kprobe_disabled(&op->kp)) + /* Disarm probes if marked disabled and not gone */ + if (kprobe_disabled(&op->kp) && !kprobe_gone(&op->kp)) arch_disarm_kprobe(&op->kp); if (kprobe_unused(&op->kp)) { /* @@ -788,14 +786,13 @@ static void kill_optimized_kprobe(struct kprobe *p) op->kp.flags &= ~KPROBE_FLAG_OPTIMIZED;

if (kprobe_unused(p)) { - /* Enqueue if it is unused */ - list_add(&op->list, &freeing_list); /* - * Remove unused probes from the hash list. After waiting - * for synchronization, this probe is reclaimed. - * (reclaiming is done by do_free_cleaned_kprobes().) + * Unused kprobe is on unoptimizing or freeing list. We move it + * to freeing_list and let the kprobe_optimizer() remove it from + * the kprobe hash list and free it. */ - hlist_del_rcu(&op->kp.hlist); + if (optprobe_queued_unopt(op)) + list_move(&op->list, &freeing_list); }

/* Don't touch the code, because it is already freed. */