2022-09-27 20:51:21

by Jiri Olsa

Subject: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

Recent commit [1] changed branch stack data indication from
br_stack pointer to sample_flags in perf_sample_data struct.

We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
bit for valid branch stack data.

[1] a9a931e26668 ("perf: Use sample_flags for branch stack")

Cc: Kan Liang <[email protected]>
Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
Signed-off-by: Jiri Olsa <[email protected]>
---
NOTE sending on top of tip/master because [1] is not
merged in bpf-next/master yet

kernel/trace/bpf_trace.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 68e5cdd24cef..1fcd1234607e 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
return -EINVAL;

+ if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
+ return -ENOENT;
+
if (unlikely(!br_stack))
return -ENOENT;

--
2.37.3

2022-09-27 21:27:11

by Peter Zijlstra

Subject: Re: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

On Tue, Sep 27, 2022 at 10:32:59PM +0200, Jiri Olsa wrote:
> Recent commit [1] changed branch stack data indication from
> br_stack pointer to sample_flags in perf_sample_data struct.
>
> We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
> bit for valid branch stack data.
>
> [1] a9a931e26668 ("perf: Use sample_flags for branch stack")
>
> Cc: Kan Liang <[email protected]>
> Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
> Signed-off-by: Jiri Olsa <[email protected]>
> ---
> NOTE sending on top of tip/master because [1] is not
> merged in bpf-next/master yet

Shall I stick this in tip/perf/core right along with [1] then?

2022-09-27 21:27:26

by Liang, Kan

Subject: Re: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

On 2022-09-27 4:32 p.m., Jiri Olsa wrote:
> Recent commit [1] changed branch stack data indication from
> br_stack pointer to sample_flags in perf_sample_data struct.
>
> We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
> bit for valid branch stack data.
>
> [1] a9a931e26668 ("perf: Use sample_flags for branch stack")
>
> Cc: Kan Liang <[email protected]>
> Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
> Signed-off-by: Jiri Olsa <[email protected]>

Thanks for the fix.

Reviewed-by: Kan Liang <[email protected]>

Thanks,
Kan

> ---
> NOTE sending on top of tip/master because [1] is not
> merged in bpf-next/master yet
>
> kernel/trace/bpf_trace.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 68e5cdd24cef..1fcd1234607e 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
> if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
> return -EINVAL;
>
> + if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
> + return -ENOENT;
> +
> if (unlikely(!br_stack))
> return -ENOENT;
>

2022-09-27 21:43:05

by Jiri Olsa

Subject: Re: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

On Tue, Sep 27, 2022 at 10:46:12PM +0200, Peter Zijlstra wrote:
> On Tue, Sep 27, 2022 at 10:32:59PM +0200, Jiri Olsa wrote:
> > Recent commit [1] changed branch stack data indication from
> > br_stack pointer to sample_flags in perf_sample_data struct.
> >
> > We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
> > bit for valid branch stack data.
> >
> > [1] a9a931e26668 ("perf: Use sample_flags for branch stack")
> >
> > Cc: Kan Liang <[email protected]>
> > Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
> > Signed-off-by: Jiri Olsa <[email protected]>
> > ---
> > NOTE sending on top of tip/master because [1] is not
> > merged in bpf-next/master yet
>
> Shall I stick this in tip/perf/core right along with [1] then?

yes, sounds good

thanks,
jirka

2022-09-27 22:07:43

by Song Liu

Subject: Re: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

> On Sep 27, 2022, at 1:32 PM, Jiri Olsa <[email protected]> wrote:
>
> Recent commit [1] changed branch stack data indication from
> br_stack pointer to sample_flags in perf_sample_data struct.
>
> We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
> bit for valid branch stack data.
>
> [1] a9a931e26668 ("perf: Use sample_flags for branch stack")
>
> Cc: Kan Liang <[email protected]>
> Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
> Signed-off-by: Jiri Olsa <[email protected]>

Thanks for the fix! I noticed the issue last week, but haven't
got time to look into it.

Song

> ---
> NOTE sending on top of tip/master because [1] is not
> merged in bpf-next/master yet
>
> kernel/trace/bpf_trace.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 68e5cdd24cef..1fcd1234607e 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
> if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
> return -EINVAL;
>
> + if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
> + return -ENOENT;
> +
> if (unlikely(!br_stack))
> return -ENOENT;
>
> --
> 2.37.3
>

2022-09-27 22:08:41

by Song Liu

Subject: Re: [PATCH -tip] bpf: Check flags for branch stack in bpf_read_branch_records helper

> On Sep 27, 2022, at 2:49 PM, Song Liu <[email protected]> wrote:
>
>
>
>> On Sep 27, 2022, at 1:32 PM, Jiri Olsa <[email protected]> wrote:
>>
>> Recent commit [1] changed branch stack data indication from
>> br_stack pointer to sample_flags in perf_sample_data struct.
>>
>> We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
>> bit for valid branch stack data.
>>
>> [1] a9a931e26668 ("perf: Use sample_flags for branch stack")
>>
>> Cc: Kan Liang <[email protected]>
>> Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
>> Signed-off-by: Jiri Olsa <[email protected]>

Acked-by: Song Liu <[email protected]>

>
> Thanks for the fix! I noticed the issue last week, but haven't
> got time to look into it.
>
> Song
>
>> ---
>> NOTE sending on top of tip/master because [1] is not
>> merged in bpf-next/master yet
>>
>> kernel/trace/bpf_trace.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
>> index 68e5cdd24cef..1fcd1234607e 100644
>> --- a/kernel/trace/bpf_trace.c
>> +++ b/kernel/trace/bpf_trace.c
>> @@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
>> if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
>> return -EINVAL;
>>
>> + if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
>> + return -ENOENT;
>> +
>> if (unlikely(!br_stack))
>> return -ENOENT;
>>
>> --
>> 2.37.3

2022-09-28 07:36:24

by tip-bot2 for Jacob Pan

Subject: [tip: perf/core] bpf: Check flags for branch stack in bpf_read_branch_records helper

The following commit has been merged into the perf/core branch of tip:

Commit-ID: cce6a2d7e0e494c453ad73e1e78bd50684f20cca
Gitweb: https://git.kernel.org/tip/cce6a2d7e0e494c453ad73e1e78bd50684f20cca
Author: Jiri Olsa <[email protected]>
AuthorDate: Tue, 27 Sep 2022 22:32:59 +02:00
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Tue, 27 Sep 2022 22:50:25 +02:00

bpf: Check flags for branch stack in bpf_read_branch_records helper

Recent commit [1] changed branch stack data indication from
br_stack pointer to sample_flags in perf_sample_data struct.

We need to check sample_flags for PERF_SAMPLE_BRANCH_STACK
bit for valid branch stack data.

[1] a9a931e26668 ("perf: Use sample_flags for branch stack")

Fixes: a9a931e26668 ("perf: Use sample_flags for branch stack")
Signed-off-by: Jiri Olsa <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Kan Liang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/trace/bpf_trace.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 68e5cdd..1fcd123 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1507,6 +1507,9 @@ BPF_CALL_4(bpf_read_branch_records, struct bpf_perf_event_data_kern *, ctx,
if (unlikely(flags & ~BPF_F_GET_BRANCH_RECORDS_SIZE))
return -EINVAL;

+ if (unlikely(!(ctx->data->sample_flags & PERF_SAMPLE_BRANCH_STACK)))
+ return -ENOENT;
+
if (unlikely(!br_stack))
return -ENOENT;