[PATCH v13 01/12] kprobes: Protect kprobe_blacklist with RCU
From: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Date: 2026-08-22 09:22:36
Also in:
linux-doc, linux-perf-users, lkml
Subsystem:
kprobes, the rest · Maintainers:
Naveen N Rao, "David S. Miller", Masami Hiramatsu, Linus Torvalds
From: Masami Hiramatsu (Google) <mhiramat@kernel.org> __within_kprobe_blacklist() traverses kprobe_blacklist without holding kprobe_mutex. When a module is unloaded, kprobe_remove_area_blacklist() removes blacklist entries and immediately frees them with kfree(). A concurrent call to within_kprobe_blacklist() can therefore dereference freed memory. Furthermore, within_kprobe_blacklist() can be called in atomic or non-preemptible contexts where the sleeping kprobe_mutex cannot be taken. Protect kprobe_blacklist with RCU. Use guard(rcu)() and list_for_each_entry_rcu() for traversal, list_add_tail_rcu() for insertions, list_del_rcu() for deletions, and kfree_rcu() to reclaim entries safely after a grace period. Assisted-by: Antigravity:gemini-3.7-flash Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> --- Changes in v13: - Newly added. --- include/linux/kprobes.h | 1 + kernel/kprobes.c | 14 ++++++++++---- 2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 8c4f3bb24429..e6de7ae55bda 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h@@ -181,6 +181,7 @@ struct kprobe_blacklist_entry { struct list_head list; unsigned long start_addr; unsigned long end_addr; + struct rcu_head rcu; }; #ifdef CONFIG_KPROBES
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index bfc89083daa9..6337da5cab9e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c@@ -1447,8 +1447,14 @@ static bool __within_kprobe_blacklist(unsigned long addr) /* * If 'kprobe_blacklist' is defined, check the address and * reject any probe registration in the prohibited area. + * Note: this can return true during transition period where + * (start_addr, end_addr) in the black list is shrinking + * but old entry has not been removed yet. This is acceptable + * because the worst case is that we reject more probes than + * we should. */ - list_for_each_entry(ent, &kprobe_blacklist, list) { + guard(rcu)(); + list_for_each_entry_rcu(ent, &kprobe_blacklist, list) { if (addr >= ent->start_addr && addr < ent->end_addr) return true; }
@@ -2509,7 +2515,7 @@ int kprobe_add_ksym_blacklist(unsigned long entry) ent->start_addr = entry; ent->end_addr = entry + size; INIT_LIST_HEAD(&ent->list); - list_add_tail(&ent->list, &kprobe_blacklist); + list_add_tail_rcu(&ent->list, &kprobe_blacklist); return (int)size; }
@@ -2603,8 +2609,8 @@ static void kprobe_remove_area_blacklist(unsigned long start, unsigned long end) list_for_each_entry_safe(ent, n, &kprobe_blacklist, list) { if (ent->start_addr < start || ent->start_addr >= end) continue; - list_del(&ent->list); - kfree(ent); + list_del_rcu(&ent->list); + kfree_rcu(ent, rcu); } }