Hi Greg and Sasha,
This patch is not able to be applied to upstream because fprobe
implementation was changed in v6.14 by commit 4346ba160409 ("fprobe:
Rewrite fprobe on function-graph tracer"). So this is only for 6.12.y.
Please tell me if I need more work for merging this fix in stable tree.
Thank you,
On Mon, 23 Feb 2026 00:26:36 +0900
"Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu <[email protected]>
>
> Clear fprobe after unregister_fprobe() for preventing double
> unregistering fprobe.
>
> Without this fix, test.d/dynevent/add_remove_tprobe_module.tc test
> case of ftracetest caused a kernel panic as below on 6.12.y.
>
> This is only happens on 6.12.y because this bug was introduced by
> commit 5ba4f58ec2de ("tracing: tprobe-events: Fix to clean up tprobe
> correctly when module unload"). This fix expects that the new fprobe
> implementation based on fgraph, but on 6.12.y, fprobe is still using
> ftrace.
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 156 at kernel/trace/ftrace.c:378
> __unregister_ftrace_function+0x154/0x170
> Modules linked in: [last unloaded: trace_events_sample]
> CPU: 0 UID: 0 PID: 156 Comm: ftracetest Not tainted 6.12.74 #1
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:__unregister_ftrace_function+0x154/0x170
> Code: 85 30 ff ff ff c6 05 fd d5 85 01 01 48 c7 c7 eb 8e 14 82 be 39 01 00
> 00 48 c7 c2 dd bd 1c 82 e8 52 12 93 00 e9 0c ff ff ff 90 <0f> 0b 90 b8 f0 ff
> ff ff 5b e9 be 8b 95 00 cc 66 66 66 66 2e 0f 1f
> RSP: 0018:ffffc900005c3b48 EFLAGS: 00010246
> RAX: 0000000000000000 RBX: ffff8880054ba818 RCX: 7a7d3ccd1e752c00
> RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff8880054ba818
> RBP: 0000000000000000 R08: 000000000000017b R09: 0000000000000000
> R10: 0000000000000002 R11: 0000000000000000 R12: ffff8880048216d0
> R13: ffff8880052f7850 R14: ffff8880054ba818 R15: ffffffff8124e160
> FS: 000000002de743c0(0000) GS:ffff88807d800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000002de8b898 CR3: 0000000005b3a000 CR4: 00000000000006b0
> Call Trace:
> <TASK>
> ftrace_shutdown+0x25/0x260
> ? __pfx_dyn_event_open+0x10/0x10
> unregister_ftrace_function+0x2a/0x140
> ? __pfx_dyn_event_open+0x10/0x10
> unregister_fprobe+0x57/0x90
> trace_fprobe_release+0x56/0x150
> dyn_event_open+0x99/0xe0
> do_dentry_open+0x14a/0x3e0
> vfs_open+0x2c/0xe0
> path_openat+0xca5/0xf10
> ? __lock_acquire+0xd38/0x2af0
> ? __create_object+0x36/0x100
> ? __create_object+0x36/0x100
> do_filp_open+0xb5/0x160
> do_sys_openat2+0x7f/0xd0
> __x64_sys_openat+0x81/0xa0
> do_syscall_64+0xec/0x1d0
> ? exc_page_fault+0x92/0x110
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x4aa9cb
> Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75
> 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff
> 0f 87 91 00 00 00 48 8b 54 24 28 64 48 2b 14 25
> RSP: 002b:00007ffce30daf50 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 000000002de79bd0 RCX: 00000000004aa9cb
> RDX: 0000000000000241 RSI: 000000002deb08f0 RDI: 00000000ffffff9c
> RBP: 000000002deb08f0 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000241
> R13: 000000002deb08f0 R14: 00007ffce30db3f8 R15: 0000000000000000
> </TASK>
> irq event stamp: 147361
> hardirqs last enabled at (147373): [<ffffffff81128511>]
> __console_unlock+0x81/0xd0
> hardirqs last disabled at (147386): [<ffffffff811284f6>]
> __console_unlock+0x66/0xd0
> softirqs last enabled at (146866): [<ffffffff8109a74f>]
> handle_softirqs+0x34f/0x3b0
> softirqs last disabled at (146861): [<ffffffff8109a956>]
> __irq_exit_rcu+0x66/0xd0
> ---[ end trace 0000000000000000 ]---
> BUG: kernel NULL pointer dereference, address: 000000000000002e
> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 8000000005af0067 P4D 8000000005af0067 PUD 55d7067 PMD 0
> Oops: Oops: 0000 [#1] PREEMPT SMP PTI
> CPU: 0 UID: 0 PID: 156 Comm: ftracetest Tainted: G W 6.12.74
> #1
> Tainted: [W]=WARN
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 1.16.3-debian-1.16.3-2 04/01/2014
> RIP: 0010:trace_fprobe_release+0x78/0x150
> Code: 4c 89 f7 e8 ba e2 ff ff ba f0 01 00 00 4c 89 f7 31 f6 e8 9b 64 8d 00
> 48 8b bb 10 02 00 00 48 85 ff 74 21 4c 8d b3 10 02 00 00 <48> 8b 77 30 31 d2
> e8 8d cf f8 ff 49 c7 06 00 00 00 00 49 c7 46 08
> RSP: 0018:ffffc900005c3be8 EFLAGS: 00010282
> RAX: ffff8880054ba818 RBX: ffff8880054ba800 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: fffffffffffffffe
> RBP: 00000000fffffff0 R08: 000000000000017b R09: 0000000000000000
> R10: ffff8880054ba818 R11: 0000000000000000 R12: ffff8880048216d0
> R13: ffff8880052f7850 R14: ffff8880054baa10 R15: ffffffff8124e160
> FS: 000000002de743c0(0000) GS:ffff88807d800000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000000000002e CR3: 0000000005b3a000 CR4: 00000000000006b0
> Call Trace:
> <TASK>
> dyn_event_open+0x99/0xe0
> do_dentry_open+0x14a/0x3e0
> vfs_open+0x2c/0xe0
> path_openat+0xca5/0xf10
> ? __lock_acquire+0xd38/0x2af0
> ? __create_object+0x36/0x100
> ? __create_object+0x36/0x100
> do_filp_open+0xb5/0x160
> do_sys_openat2+0x7f/0xd0
> __x64_sys_openat+0x81/0xa0
> do_syscall_64+0xec/0x1d0
> ? exc_page_fault+0x92/0x110
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x4aa9cb
> Code: 25 00 00 41 00 3d 00 00 41 00 74 4b 64 8b 04 25 18 00 00 00 85 c0 75
> 67 44 89 e2 48 89 ee bf 9c ff ff ff b8 01 01 00 00 0f 05 <48> 3d 00 f0 ff ff
> 0f 87 91 00 00 00 48 8b 54 24 28 64 48 2b 14 25
> RSP: 002b:00007ffce30daf50 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 000000002de79bd0 RCX: 00000000004aa9cb
> RDX: 0000000000000241 RSI: 000000002deb08f0 RDI: 00000000ffffff9c
> RBP: 000000002deb08f0 R08: 0000000000000000 R09: 0000000000000000
> R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000241
> R13: 000000002deb08f0 R14: 00007ffce30db3f8 R15: 0000000000000000
> </TASK>
> Modules linked in: [last unloaded: trace_events_sample]
> CR2: 000000000000002e
> ---[ end trace 0000000000000000 ]---
>
> Fixes: 5ba4f58ec2de ("tracing: tprobe-events: Fix to clean up tprobe
> correctly when module unload")
> Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
> ---
> kernel/trace/trace_fprobe.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/trace/trace_fprobe.c b/kernel/trace/trace_fprobe.c
> index 440dbfa6bbfd..2cf5036c825d 100644
> --- a/kernel/trace/trace_fprobe.c
> +++ b/kernel/trace/trace_fprobe.c
> @@ -984,6 +984,7 @@ static int __tracepoint_probe_module_cb(struct
> notifier_block *self,
> }
> } else if (val == MODULE_STATE_GOING && tp_mod->mod == tf->mod)
> {
> unregister_fprobe(&tf->fp);
> + memset(&tf->fp, 0, sizeof(tf->fp));
> if (trace_fprobe_is_tracepoint(tf)) {
> tracepoint_probe_unregister(tf->tpoint,
> tf->tpoint->probestub, NULL);
>
--
Masami Hiramatsu (Google) <[email protected]>
