2024-05-25 18:22:24

by Carlos López

Subject: [PATCH] tracing/probes: fix error check in parse_btf_field()

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.

Fixes: c440adfbe3025 ("tracing/probes: Support BTF based data structure field access")
Signed-off-by: Carlos López <[email protected]>
---
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

2024-05-26 10:17:19

by Masami Hiramatsu

Subject: Re: [PATCH] tracing/probes: fix error check in parse_btf_field()

On Sat, 25 May 2024 20:21:32 +0200
Carlos López <[email protected]> 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@kernel/trace/trace_probe.h ?

Thank you,

> Fixes: c440adfbe3025 ("tracing/probes: Support BTF based data structure field access")
> Signed-off-by: Carlos López <[email protected]>
> ---
> 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
>


--
Masami Hiramatsu (Google) <[email protected]>

2024-05-26 12:28:20

by Carlos López

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 <[email protected]> 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@kernel/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 <[email protected]>
>> ---
>> 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

2024-05-26 23:13:17

by Masami Hiramatsu

Subject: Re: [PATCH] tracing/probes: fix error check in parse_btf_field()

On Sun, 26 May 2024 14:27:56 +0200
Carlos López <[email protected]> wrote:

>
> Hi,
>
> On 26/5/24 12:17, Masami Hiramatsu (Google) wrote:
> > On Sat, 25 May 2024 20:21:32 +0200
> > Carlos López <[email protected]> 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@kernel/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.

Good point, it sounds reasonable.

Thanks!

>
> Best,
> Carlos
>
> > Thank you,
> >
> >> Fixes: c440adfbe3025 ("tracing/probes: Support BTF based data structure field access")
> >> Signed-off-by: Carlos López <[email protected]>
> >> ---
> >> 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


--
Masami Hiramatsu (Google) <[email protected]>