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Message-ID: <ff240b23-4143-4171-8dcc-1fdbf1802e8c@suse.de>
Date: Sun, 26 May 2024 14:27:56 +0200
From: Carlos López <clopez@...e.de>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Alan Maguire <alan.maguire@...cle.com>,
"open list:TRACING" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tracing/probes: fix error check in parse_btf_field()
Hi,
On 26/5/24 12:17, Masami Hiramatsu (Google) wrote:
> On Sat, 25 May 2024 20:21:32 +0200
> Carlos López <clopez@...e.de> wrote:
>
>> btf_find_struct_member() might return NULL or an error via the
>> ERR_PTR() macro. However, its caller in parse_btf_field() only checks
>> for the NULL condition. Fix this by using IS_ERR() and returning the
>> error up the stack.
>>
>
> Thanks for finding it!
> I think this requires new error message for error_log file.
> Can you add the log as
>
> trace_probe_log_err(ctx->offset, BTF_ERROR);
>
> And define BTF_ERROR in ERRORS@...nel/trace/trace_probe.h ?
Sounds good, but should we perhaps reuse BAD_BTF_TID?
```
C(BAD_BTF_TID, "Failed to get BTF type info."),\
```
`btf_find_struct_member()` fails if `type` is not a struct or if it runs
OOM while allocating the anon stack, so it seems appropriate.
Best,
Carlos
> Thank you,
>
>> Fixes: c440adfbe3025 ("tracing/probes: Support BTF based data structure field access")
>> Signed-off-by: Carlos López <clopez@...e.de>
>> ---
>> kernel/trace/trace_probe.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
>> index 5e263c141574..5417e9712157 100644
>> --- a/kernel/trace/trace_probe.c
>> +++ b/kernel/trace/trace_probe.c
>> @@ -554,6 +554,8 @@ static int parse_btf_field(char *fieldname, const struct btf_type *type,
>> anon_offs = 0;
>> field = btf_find_struct_member(ctx->btf, type, fieldname,
>> &anon_offs);
>> + if (IS_ERR(field))
>> + return PTR_ERR(field);
>> if (!field) {
>> trace_probe_log_err(ctx->offset, NO_BTF_FIELD);
>> return -ENOENT;
>> --
>> 2.35.3
>>
>
>
--
Carlos López
Security Engineer
SUSE Software Solutions
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