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kprobes: Protect kprobe_blacklist with RCU

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__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: 376e242429 ("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>
This commit is contained in:
Masami Hiramatsu (Google)
2026-08-30 23:27:23 +09:00
parent 86b7a239ec
commit 0c4256196b
2 changed files with 11 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/kprobes.h
View File

@@ -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

14
kernel/kprobes.c
View File

@@ -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);
}
}