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

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

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhiramat@kernel.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@huawei.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@kernel.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);

Re: [PATCH] kprobes: avoid crash when rmmod/insmod after ftrace killed

[Steven Rostedt]

On Wed,  3 Dec 2025 14:24:35 +0900
"Masami Hiramatsu (Google)" <mhiramat@kernel.org> wrote:

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

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve