[PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Leo Yan]

Commit a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
causes segmentation fault when run the "perf mem record" command in
unprivileged mode, the output log is:

  $ ./perf mem record --all-user -o perf_test.data -- ./test_program
  Error:
  Access to performance monitoring and observability operations is limited.
  Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
  access to performance monitoring and observability operations for processes
  without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability.
  More information can be found at 'Perf events and tool security' document:
  https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
  perf_event_paranoid setting is 4:
    -1: Allow use of (almost) all events by all users
        Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
  >= 0: Disallow raw and ftrace function tracepoint access
  >= 1: Disallow CPU event access
  >= 2: Disallow kernel profiling
  To make the adjusted perf_event_paranoid setting permanent preserve it
  in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
  perf: Segmentation fault
  Obtained 16 stack frames.
  ./perf(dump_stack+0x31) [0x55b7aa1e8070]
  ./perf(sighandler_dump_stack+0x36) [0x55b7aa1e815e]
  ./perf(+0xc9120) [0x55b7aa0a9120]
  /lib/x86_64-linux-gnu/libc.so.6(+0x4251f) [0x7fd03ef8151f]
  ./perf(+0xccaca) [0x55b7aa0acaca]
  ./perf(+0xcf4ab) [0x55b7aa0af4ab]
  ./perf(cmd_record+0xd50) [0x55b7aa0b28df]
  ./perf(+0x112f77) [0x55b7aa0f2f77]
  ./perf(cmd_mem+0x53b) [0x55b7aa0f406c]
  ./perf(+0x19979c) [0x55b7aa17979c]
  ./perf(+0x199a37) [0x55b7aa179a37]
  ./perf(+0x199b95) [0x55b7aa179b95]
  ./perf(main+0x2c7) [0x55b7aa179fbd]
  /lib/x86_64-linux-gnu/libc.so.6(+0x29d8f) [0x7fd03ef68d8f]
  /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x7f) [0x7fd03ef68e3f]
  ./perf(_start+0x24) [0x55b7aa089974]
  Segmentation fault (core dumped)

In the unprivileged mode perf fails to open PMU event, the function
record__open() returns error and "session->evlist" is NULL; this leads
to segmentation fault when iterates "session->evlist" in the function
record__read_lost_samples().

This patch checks "session->evlist" in record__read_lost_samples(), if
"session->evlist" is NULL then the function directly bails out to avoid
segmentation fault.

Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/perf/builtin-record.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 02e38f50a138..012b46dd4999 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;
 
+	/* No any event is opened, directly bail out */
+	if (!session->evlist)
+		return;
+
 	lost = zalloc(PERF_SAMPLE_MAX_SIZE);
 	if (lost == NULL) {
 		pr_debug("Memory allocation failed\n");
-- 
2.34.1

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Namhyung Kim]

Hi Leo,

On Sat, Sep 24, 2022 at 4:34 AM Leo Yan <leo.yan@linaro.org> wrote:
>
> Commit a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> causes segmentation fault when run the "perf mem record" command in
> unprivileged mode, the output log is:
>
>   $ ./perf mem record --all-user -o perf_test.data -- ./test_program
>   Error:
>   Access to performance monitoring and observability operations is limited.
>   Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
>   access to performance monitoring and observability operations for processes
>   without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability.
>   More information can be found at 'Perf events and tool security' document:
>   https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
>   perf_event_paranoid setting is 4:
>     -1: Allow use of (almost) all events by all users
>         Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
>   >= 0: Disallow raw and ftrace function tracepoint access
>   >= 1: Disallow CPU event access
>   >= 2: Disallow kernel profiling
>   To make the adjusted perf_event_paranoid setting permanent preserve it
>   in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
>   perf: Segmentation fault
>   Obtained 16 stack frames.
>   ./perf(dump_stack+0x31) [0x55b7aa1e8070]
>   ./perf(sighandler_dump_stack+0x36) [0x55b7aa1e815e]
>   ./perf(+0xc9120) [0x55b7aa0a9120]
>   /lib/x86_64-linux-gnu/libc.so.6(+0x4251f) [0x7fd03ef8151f]
>   ./perf(+0xccaca) [0x55b7aa0acaca]
>   ./perf(+0xcf4ab) [0x55b7aa0af4ab]
>   ./perf(cmd_record+0xd50) [0x55b7aa0b28df]
>   ./perf(+0x112f77) [0x55b7aa0f2f77]
>   ./perf(cmd_mem+0x53b) [0x55b7aa0f406c]
>   ./perf(+0x19979c) [0x55b7aa17979c]
>   ./perf(+0x199a37) [0x55b7aa179a37]
>   ./perf(+0x199b95) [0x55b7aa179b95]
>   ./perf(main+0x2c7) [0x55b7aa179fbd]
>   /lib/x86_64-linux-gnu/libc.so.6(+0x29d8f) [0x7fd03ef68d8f]
>   /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x7f) [0x7fd03ef68e3f]
>   ./perf(_start+0x24) [0x55b7aa089974]
>   Segmentation fault (core dumped)
>
> In the unprivileged mode perf fails to open PMU event, the function
> record__open() returns error and "session->evlist" is NULL; this leads
> to segmentation fault when iterates "session->evlist" in the function
> record__read_lost_samples().
>
> This patch checks "session->evlist" in record__read_lost_samples(), if
> "session->evlist" is NULL then the function directly bails out to avoid
> segmentation fault.
>
> Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> Signed-off-by: Leo Yan <leo.yan@linaro.org>

Thanks for the fix and sorry for the inconvenience.
Actually I sent the same fix a few weeks ago.

https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org

Thanks,
Namhyung


> ---
>  tools/perf/builtin-record.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index 02e38f50a138..012b46dd4999 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;
>
> +       /* No any event is opened, directly bail out */
> +       if (!session->evlist)
> +               return;
> +
>         lost = zalloc(PERF_SAMPLE_MAX_SIZE);
>         if (lost == NULL) {
>                 pr_debug("Memory allocation failed\n");
> --
> 2.34.1
>

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Leo Yan]

Hi Namhyung,

On Sat, Sep 24, 2022 at 09:52:09AM -0700, Namhyung Kim wrote:

[...]

> > In the unprivileged mode perf fails to open PMU event, the function
> > record__open() returns error and "session->evlist" is NULL; this leads
> > to segmentation fault when iterates "session->evlist" in the function
> > record__read_lost_samples().
> >
> > This patch checks "session->evlist" in record__read_lost_samples(), if
> > "session->evlist" is NULL then the function directly bails out to avoid
> > segmentation fault.
> >
> > Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> 
> Thanks for the fix and sorry for the inconvenience.
> Actually I sent the same fix a few weeks ago.
> 
> https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org

Thanks a lot for the info and fix.  The patch in above link looks good
to me!  Please ignore this one.

Leo

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Arnaldo Carvalho de Melo]

Em Sat, Sep 24, 2022 at 09:52:09AM -0700, Namhyung Kim escreveu:
> Hi Leo,
> 
> On Sat, Sep 24, 2022 at 4:34 AM Leo Yan <leo.yan@linaro.org> wrote:
> >
> > Commit a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > causes segmentation fault when run the "perf mem record" command in
> > unprivileged mode, the output log is:
> >
> >   $ ./perf mem record --all-user -o perf_test.data -- ./test_program
> >   Error:
> >   Access to performance monitoring and observability operations is limited.
> >   Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
> >   access to performance monitoring and observability operations for processes
> >   without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability.
> >   More information can be found at 'Perf events and tool security' document:
> >   https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
> >   perf_event_paranoid setting is 4:
> >     -1: Allow use of (almost) all events by all users
> >         Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
> >   >= 0: Disallow raw and ftrace function tracepoint access
> >   >= 1: Disallow CPU event access
> >   >= 2: Disallow kernel profiling
> >   To make the adjusted perf_event_paranoid setting permanent preserve it
> >   in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
> >   perf: Segmentation fault
> >   Obtained 16 stack frames.
> >   ./perf(dump_stack+0x31) [0x55b7aa1e8070]
> >   ./perf(sighandler_dump_stack+0x36) [0x55b7aa1e815e]
> >   ./perf(+0xc9120) [0x55b7aa0a9120]
> >   /lib/x86_64-linux-gnu/libc.so.6(+0x4251f) [0x7fd03ef8151f]
> >   ./perf(+0xccaca) [0x55b7aa0acaca]
> >   ./perf(+0xcf4ab) [0x55b7aa0af4ab]
> >   ./perf(cmd_record+0xd50) [0x55b7aa0b28df]
> >   ./perf(+0x112f77) [0x55b7aa0f2f77]
> >   ./perf(cmd_mem+0x53b) [0x55b7aa0f406c]
> >   ./perf(+0x19979c) [0x55b7aa17979c]
> >   ./perf(+0x199a37) [0x55b7aa179a37]
> >   ./perf(+0x199b95) [0x55b7aa179b95]
> >   ./perf(main+0x2c7) [0x55b7aa179fbd]
> >   /lib/x86_64-linux-gnu/libc.so.6(+0x29d8f) [0x7fd03ef68d8f]
> >   /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0x7f) [0x7fd03ef68e3f]
> >   ./perf(_start+0x24) [0x55b7aa089974]
> >   Segmentation fault (core dumped)
> >
> > In the unprivileged mode perf fails to open PMU event, the function
> > record__open() returns error and "session->evlist" is NULL; this leads
> > to segmentation fault when iterates "session->evlist" in the function
> > record__read_lost_samples().
> >
> > This patch checks "session->evlist" in record__read_lost_samples(), if
> > "session->evlist" is NULL then the function directly bails out to avoid
> > segmentation fault.
> >
> > Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> 
> Thanks for the fix and sorry for the inconvenience.
> Actually I sent the same fix a few weeks ago.
> 
> https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org

collecting it now, and adding that Fixes from Leo's patch, ok?

- Arnaldo
 
> Thanks,
> Namhyung
> 
> 
> > ---
> >  tools/perf/builtin-record.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index 02e38f50a138..012b46dd4999 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;
> >
> > +       /* No any event is opened, directly bail out */
> > +       if (!session->evlist)
> > +               return;
> > +
> >         lost = zalloc(PERF_SAMPLE_MAX_SIZE);
> >         if (lost == NULL) {
> >                 pr_debug("Memory allocation failed\n");
> > --
> > 2.34.1
> >

-- 

- Arnaldo

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Arnaldo Carvalho de Melo]

Em Sun, Sep 25, 2022 at 09:12:37AM +0800, Leo Yan escreveu:
> Hi Namhyung,
> 
> On Sat, Sep 24, 2022 at 09:52:09AM -0700, Namhyung Kim wrote:
> 
> [...]
> 
> > > In the unprivileged mode perf fails to open PMU event, the function
> > > record__open() returns error and "session->evlist" is NULL; this leads
> > > to segmentation fault when iterates "session->evlist" in the function
> > > record__read_lost_samples().
> > >
> > > This patch checks "session->evlist" in record__read_lost_samples(), if
> > > "session->evlist" is NULL then the function directly bails out to avoid
> > > segmentation fault.
> > >
> > > Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > 
> > Thanks for the fix and sorry for the inconvenience.
> > Actually I sent the same fix a few weeks ago.
> > 
> > https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org
> 
> Thanks a lot for the info and fix.  The patch in above link looks good
> to me!  Please ignore this one.

Took that as an Acked-by: Leo, thanks!

- Arnaldo

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Leo Yan]

On Mon, Sep 26, 2022 at 01:59:29PM +0100, Arnaldo Carvalho de Melo wrote:

[...]

> > > Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > 
> > Thanks for the fix and sorry for the inconvenience.
> > Actually I sent the same fix a few weeks ago.
> > 
> > https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org
> 
> collecting it now, and adding that Fixes from Leo's patch, ok?

Yeah, I think it's good to add Fixes tag.  Just remind, actually
Namhyung has mentioned Fixed tag in above link:

"I didn't add a Fixes tag as it's not sent to Linus yet. But in case you want it.

  Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
"

Thanks,
Leo

Re: [PATCH] perf record: Fix segmentation fault in record__read_lost_samples()

[Arnaldo Carvalho de Melo]

Em Mon, Sep 26, 2022 at 10:54:43PM +0800, Leo Yan escreveu:
> On Mon, Sep 26, 2022 at 01:59:29PM +0100, Arnaldo Carvalho de Melo wrote:
> 
> [...]
> 
> > > > Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> > > > Signed-off-by: Leo Yan <leo.yan@linaro.org>
> > > 
> > > Thanks for the fix and sorry for the inconvenience.
> > > Actually I sent the same fix a few weeks ago.
> > > 
> > > https://lore.kernel.org/r/20220909235024.278281-1-namhyung@kernel.org
> > 
> > collecting it now, and adding that Fixes from Leo's patch, ok?
> 
> Yeah, I think it's good to add Fixes tag.  Just remind, actually
> Namhyung has mentioned Fixed tag in above link:
> 
> "I didn't add a Fixes tag as it's not sent to Linus yet. But in case you want it.
> 
>   Fixes: a49aa8a54e86 ("perf record: Read and inject LOST_SAMPLES events")
> "

I'll add it.

Sometimes I think about combining fixes with patches in my tree that
didn't made it into Linus tree yet, so that we avoid having problems
with 'git bisect', but I also try not to rebase acme/perf/core.

Perhaps in the future 'git bisect' will look at Fixes: tags :-)

- Arnaldo