2022-09-23 17:37:39

by Namhyung Kim

Subject: [PATCH 1/4] perf record: Fix a segfault in record__read_lost_samples()

When it fails to open events record__open() returns without setting the
session->evlist. Then it gets a segfault in the function trying to read
lost sample counts. You can easily reproduce it as a normal user like:

$ perf record -p 1 true
...
perf: Segmentation fault
...

Skip the function if it has no evlist. And add more protection for evsels
which are not properly initialized.

Signed-off-by: Namhyung Kim <[email protected]>
---
tools/perf/builtin-record.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 741e763436ca..f4f1619199e5 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1888,6 +1888,10 @@ static void record__read_lost_samples(struct record *rec)
struct perf_record_lost_samples *lost;
struct evsel *evsel;

+ /* there was an error during record__open */
+ if (session->evlist == NULL)
+ return;
+
lost = zalloc(PERF_SAMPLE_MAX_SIZE);
if (lost == NULL) {
pr_debug("Memory allocation failed\n");
@@ -1899,6 +1903,8 @@ static void record__read_lost_samples(struct record *rec)
evlist__for_each_entry(session->evlist, evsel) {
struct xyarray *xy = evsel->core.sample_id;

+ if (xy == NULL || evsel->core.fd == NULL)
+ continue;
if (xyarray__max_x(evsel->core.fd) != xyarray__max_x(xy) ||
xyarray__max_y(evsel->core.fd) != xyarray__max_y(xy)) {
pr_debug("Unmatched FD vs. sample ID: skip reading LOST count\n");
--
2.37.3.998.g577e59143f-goog

2022-09-24 00:19:14

by Ian Rogers

Subject: Re: [PATCH 1/4] perf record: Fix a segfault in record__read_lost_samples()

On Fri, Sep 23, 2022 at 10:32 AM Namhyung Kim <[email protected]> wrote:
>
> When it fails to open events record__open() returns without setting the
> session->evlist. Then it gets a segfault in the function trying to read
> lost sample counts. You can easily reproduce it as a normal user like:
>
> $ perf record -p 1 true
> ...
> perf: Segmentation fault
> ...
>
> Skip the function if it has no evlist. And add more protection for evsels
> which are not properly initialized.
>
> Signed-off-by: Namhyung Kim <[email protected]>

Acked-by: Ian Rogers <[email protected]>

Thanks,
Ian

> ---
> tools/perf/builtin-record.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 741e763436ca..f4f1619199e5 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1888,6 +1888,10 @@ static void record__read_lost_samples(struct record *rec)
> struct perf_record_lost_samples *lost;
> struct evsel *evsel;
>
> + /* there was an error during record__open */
> + if (session->evlist == NULL)
> + return;
> +
> lost = zalloc(PERF_SAMPLE_MAX_SIZE);
> if (lost == NULL) {
> pr_debug("Memory allocation failed\n");
> @@ -1899,6 +1903,8 @@ static void record__read_lost_samples(struct record *rec)
> evlist__for_each_entry(session->evlist, evsel) {
> struct xyarray *xy = evsel->core.sample_id;
>
> + if (xy == NULL || evsel->core.fd == NULL)
> + continue;
> if (xyarray__max_x(evsel->core.fd) != xyarray__max_x(xy) ||
> xyarray__max_y(evsel->core.fd) != xyarray__max_y(xy)) {
> pr_debug("Unmatched FD vs. sample ID: skip reading LOST count\n");
> --
> 2.37.3.998.g577e59143f-goog
>

2022-09-25 01:54:12

by Leo Yan

Subject: Re: [PATCH 1/4] perf record: Fix a segfault in record__read_lost_samples()

On Fri, Sep 23, 2022 at 10:31:39AM -0700, Namhyung Kim wrote:
> When it fails to open events record__open() returns without setting the
> session->evlist. Then it gets a segfault in the function trying to read
> lost sample counts. You can easily reproduce it as a normal user like:
>
> $ perf record -p 1 true
> ...
> perf: Segmentation fault
> ...
>
> Skip the function if it has no evlist. And add more protection for evsels
> which are not properly initialized.
>
> Signed-off-by: Namhyung Kim <[email protected]>

Tested-by: Leo Yan <[email protected]>