linux-kernel - [PATCH] kprobes: avoid crash when rmmod/insmod after ftrace killed

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Message-ID:  <176473947565.1727781.13110060700668331950.stgit@mhiramat.tok.corp.google.com>
Date: Wed,  3 Dec 2025 14:24:35 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: LKML <linux-kernel@...r.kernel.org>,
	Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
	Ye Bin <yebin@...weicloud.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Naveen N Rao <naveen@...nel.org>,
	"David S . Miller" <davem@...emloft.net>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	yebin10@...wei.com
Subject: [PATCH] kprobes: avoid crash when rmmod/insmod after ftrace killed

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

After we hit ftrace is killed by some errors, the kernel crash if
we remove modules in which kprobe probes.

BUG: unable to handle page fault for address: fffffbfff805000d
PGD 817fcc067 P4D 817fcc067 PUD 817fc8067 PMD 101555067 PTE 0
Oops: Oops: 0000 [#1] SMP KASAN PTI
CPU: 4 UID: 0 PID: 2012 Comm: rmmod Tainted: G        W  OE
Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
RIP: 0010:kprobes_module_callback+0x89/0x790
RSP: 0018:ffff88812e157d30 EFLAGS: 00010a02
RAX: 1ffffffff805000d RBX: dffffc0000000000 RCX: ffffffff86a8de90
RDX: ffffed1025c2af9b RSI: 0000000000000008 RDI: ffffffffc0280068
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed1025c2af9a
R10: ffff88812e157cd7 R11: 205d323130325420 R12: 0000000000000002
R13: ffffffffc0290488 R14: 0000000000000002 R15: ffffffffc0280040
FS:  00007fbc450dd740(0000) GS:ffff888420331000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: fffffbfff805000d CR3: 000000010f624000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 notifier_call_chain+0xc6/0x280
 blocking_notifier_call_chain+0x60/0x90
 __do_sys_delete_module.constprop.0+0x32a/0x4e0
 do_syscall_64+0x5d/0xfa0
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

This is because the kprobe on ftrace does not correctly handles
the kprobe_ftrace_disabled flag set by ftrace_kill().

To prevent this error, check kprobe_ftrace_disabled in
__disarm_kprobe_ftrace() and skip all ftrace related operations.

Reported-by: Ye Bin <yebin10@...wei.com>
Closes: https://lore.kernel.org/all/20251125020536.2484381-1-yebin@huaweicloud.com/
Fixes: ae6aa16fdc16 ("kprobes: introduce ftrace based optimization")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/kprobes.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ab8f9fc1f0d1..17d451553389 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1104,6 +1104,10 @@ static int __disarm_kprobe_ftrace(struct kprobe *p, struct ftrace_ops *ops,
 	int ret;
 
 	lockdep_assert_held(&kprobe_mutex);
+	if (unlikely(kprobe_ftrace_disabled)) {
+		/* Now ftrace is disabled forever, disarm is already done. */
+		return 0;
+	}
 
 	if (*cnt == 1) {
 		ret = unregister_ftrace_function(ops);