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SubjectRe: [PATCH] tracing/eprobe: Fix warning in filter creation
On Tue,  8 Nov 2022 17:21:47 -0300
Rafael Mendonca <rafaelmendsr@gmail.com> wrote:

> The filter pointer (filterp) passed to create_filter() function must be a
> pointer that references a NULL pointer, otherwise, we get a warning when
> adding a filter option to the event probe:
>
> root@localhost:/sys/kernel/tracing# echo 'e:egroup/stat_runtime_4core sched/sched_stat_runtime \
> runtime=$runtime:u32 if cpu < 4' >> dynamic_events
> [ 5034.340439] ------------[ cut here ]------------
> [ 5034.341258] WARNING: CPU: 0 PID: 223 at kernel/trace/trace_events_filter.c:1939 create_filter+0x1db/0x250
> [...] stripped
> [ 5034.345518] RIP: 0010:create_filter+0x1db/0x250
> [...] stripped
> [ 5034.351604] Call Trace:
> [ 5034.351803] <TASK>
> [ 5034.351959] ? process_preds+0x1b40/0x1b40
> [ 5034.352241] ? rcu_read_lock_bh_held+0xd0/0xd0
> [ 5034.352604] ? kasan_set_track+0x29/0x40
> [ 5034.352904] ? kasan_save_alloc_info+0x1f/0x30
> [ 5034.353264] create_event_filter+0x38/0x50
> [ 5034.353573] __trace_eprobe_create+0x16f4/0x1d20
> [ 5034.353964] ? eprobe_dyn_event_release+0x360/0x360
> [ 5034.354363] ? mark_held_locks+0xa6/0xf0
> [ 5034.354684] ? _raw_spin_unlock_irqrestore+0x35/0x60
> [ 5034.355105] ? trace_hardirqs_on+0x41/0x120
> [ 5034.355417] ? _raw_spin_unlock_irqrestore+0x35/0x60
> [ 5034.355751] ? __create_object+0x5b7/0xcf0
> [ 5034.356027] ? lock_is_held_type+0xaf/0x120
> [ 5034.356362] ? rcu_read_lock_bh_held+0xb0/0xd0
> [ 5034.356716] ? rcu_read_lock_bh_held+0xd0/0xd0
> [ 5034.357084] ? kasan_set_track+0x29/0x40
> [ 5034.357411] ? kasan_save_alloc_info+0x1f/0x30
> [ 5034.357715] ? __kasan_kmalloc+0xb8/0xc0
> [ 5034.357985] ? write_comp_data+0x2f/0x90
> [ 5034.358302] ? __sanitizer_cov_trace_pc+0x25/0x60
> [ 5034.358691] ? argv_split+0x381/0x460
> [ 5034.358949] ? write_comp_data+0x2f/0x90
> [ 5034.359240] ? eprobe_dyn_event_release+0x360/0x360
> [ 5034.359620] trace_probe_create+0xf6/0x110
> [ 5034.359940] ? trace_probe_match_command_args+0x240/0x240
> [ 5034.360376] eprobe_dyn_event_create+0x21/0x30
> [ 5034.360709] create_dyn_event+0xf3/0x1a0
> [ 5034.360983] trace_parse_run_command+0x1a9/0x2e0
> [ 5034.361297] ? dyn_event_release+0x500/0x500
> [ 5034.361591] dyn_event_write+0x39/0x50
> [ 5034.361851] vfs_write+0x311/0xe50
> [ 5034.362091] ? dyn_event_seq_next+0x40/0x40
> [ 5034.362376] ? kernel_write+0x5b0/0x5b0
> [ 5034.362637] ? write_comp_data+0x2f/0x90
> [ 5034.362937] ? __sanitizer_cov_trace_pc+0x25/0x60
> [ 5034.363258] ? ftrace_syscall_enter+0x544/0x840
> [ 5034.363563] ? write_comp_data+0x2f/0x90
> [ 5034.363837] ? __sanitizer_cov_trace_pc+0x25/0x60
> [ 5034.364156] ? write_comp_data+0x2f/0x90
> [ 5034.364468] ? write_comp_data+0x2f/0x90
> [ 5034.364770] ksys_write+0x158/0x2a0
> [ 5034.365022] ? __ia32_sys_read+0xc0/0xc0
> [ 5034.365344] __x64_sys_write+0x7c/0xc0
> [ 5034.365669] ? syscall_enter_from_user_mode+0x53/0x70
> [ 5034.366084] do_syscall_64+0x60/0x90
> [ 5034.366356] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> [ 5034.366767] RIP: 0033:0x7ff0b43938f3
> [...] stripped
> [ 5034.371892] </TASK>
> [ 5034.374720] ---[ end trace 0000000000000000 ]---
>
> Fixes: 752be5c5c910 ("tracing/eprobe: Add eprobe filter support")
> Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thanks!

> ---
> kernel/trace/trace_eprobe.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> index 5dd0617e5df6..c2153bf59936 100644
> --- a/kernel/trace/trace_eprobe.c
> +++ b/kernel/trace/trace_eprobe.c
> @@ -900,7 +900,7 @@ static int trace_eprobe_tp_update_arg(struct trace_eprobe *ep, const char *argv[
>
> static int trace_eprobe_parse_filter(struct trace_eprobe *ep, int argc, const char *argv[])
> {
> - struct event_filter *dummy;
> + struct event_filter *dummy = NULL;
> int i, ret, len = 0;
> char *p;
>
> --
> 2.34.1
>


--
Masami Hiramatsu (Google) <mhiramat@kernel.org>

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