diff options
| author | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2026-08-30 23:27:23 +0900 |
|---|---|---|
| committer | Masami Hiramatsu (Google) <mhiramat@kernel.org> | 2026-09-03 09:04:25 +0900 |
| commit | 0c4256196b3a105307e2235fbfd85e768bbcdd0f (patch) | |
| tree | 9d98ca6dae51194795d4865fd8e2e6e9ec9642e8 | |
| parent | 86b7a239ec6b14a7544200ede85474c6f5526049 (diff) | |
kprobes: Protect kprobe_blacklist with RCU
__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.
Link: https://lore.kernel.org/all/178810004323.64882.16493230858653316962.stgit@devnote2/
Fixes: 376e242429bf ("kprobes: Introduce NOKPROBE_SYMBOL() macro to maintain kprobes blacklist")
Cc: stable@vger.kernel.org
Reported-by: Sashiko <sashiko-bot@kernel.org>
Closes: https://lore.kernel.org/all/20260807155802.F06041F000E9@smtp.kernel.org/
Assisted-by: Antigravity:gemini-3.7-flash
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
| -rw-r--r-- | include/linux/kprobes.h | 1 | ||||
| -rw-r--r-- | 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); } } |