2020-08-05 07:58:20

by Alexey Budankov

Subject: [PATCH v1] perf/core: take over CAP_SYS_PTRACE creds to CAP_PERFMON cap

Open access to per-process monitoring for CAP_PERFMON only
privileged processes [1]. Extend ptrace_may_access() check
in perf_events subsystem with perfmon_capable() to simplify
user experience and make monitoring more secure by reducing
attack surface.

[1] https://lore.kernel.org/lkml/[email protected]/

Signed-off-by: Alexey Budankov <[email protected]>
---
kernel/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 856d98c36f56..f50d528af444 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11587,7 +11587,7 @@ SYSCALL_DEFINE5(perf_event_open,
goto err_task;

/*
- * Reuse ptrace permission checks for now.
+ * Preserve ptrace permission check for backwards compatibility.
*
* We must hold exec_update_mutex across this and any potential
* perf_install_in_context() call for this new event to
@@ -11595,7 +11595,7 @@ SYSCALL_DEFINE5(perf_event_open,
* perf_event_exit_task() that could imply).
*/
err = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
+ if (!perfmon_capable() && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
goto err_cred;
}

--
2.24.1

2020-08-06 17:15:03

by tip-bot2 for Alexey Makhalov

Subject: [tip: perf/urgent] perf/core: Take over CAP_SYS_PTRACE creds to CAP_PERFMON capability

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

Commit-ID: 45fd22da97c6125d8d0d35bd1791e7c0c4175279
Gitweb: https://git.kernel.org/tip/45fd22da97c6125d8d0d35bd1791e7c0c4175279
Author: Alexey Budankov <[email protected]>
AuthorDate: Wed, 05 Aug 2020 10:56:56 +03:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Thu, 06 Aug 2020 15:03:20 +02:00

perf/core: Take over CAP_SYS_PTRACE creds to CAP_PERFMON capability

Open access to per-process monitoring for CAP_PERFMON only
privileged processes [1]. Extend ptrace_may_access() check
in perf_events subsystem with perfmon_capable() to simplify
user experience and make monitoring more secure by reducing
attack surface.

[1] https://lore.kernel.org/lkml/[email protected]/

Signed-off-by: Alexey Budankov <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/events/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 78e69e1..41e0cef 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11689,7 +11689,7 @@ SYSCALL_DEFINE5(perf_event_open,
goto err_task;

/*
- * Reuse ptrace permission checks for now.
+ * Preserve ptrace permission check for backwards compatibility.
*
* We must hold exec_update_mutex across this and any potential
* perf_install_in_context() call for this new event to
@@ -11697,7 +11697,7 @@ SYSCALL_DEFINE5(perf_event_open,
* perf_event_exit_task() that could imply).
*/
err = -EACCES;
- if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
+ if (!perfmon_capable() && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
goto err_cred;
}

2020-08-06 17:42:06

by Arnaldo Carvalho de Melo

Subject: Re: [PATCH v1] perf/core: take over CAP_SYS_PTRACE creds to CAP_PERFMON cap

Em Wed, Aug 05, 2020 at 10:56:56AM +0300, Alexey Budankov escreveu:
>
> Open access to per-process monitoring for CAP_PERFMON only
> privileged processes [1]. Extend ptrace_may_access() check
> in perf_events subsystem with perfmon_capable() to simplify
> user experience and make monitoring more secure by reducing
> attack surface.


Acked-by: Arnaldo Carvalho de Melo <[email protected]>

Peter, can you pick up this one? You said it was ok last time we
discussed this.

- Arnaldo

> [1] https://lore.kernel.org/lkml/[email protected]/
>
> Signed-off-by: Alexey Budankov <[email protected]>
> ---
> kernel/events/core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index 856d98c36f56..f50d528af444 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -11587,7 +11587,7 @@ SYSCALL_DEFINE5(perf_event_open,
> goto err_task;
>
> /*
> - * Reuse ptrace permission checks for now.
> + * Preserve ptrace permission check for backwards compatibility.
> *
> * We must hold exec_update_mutex across this and any potential
> * perf_install_in_context() call for this new event to
> @@ -11595,7 +11595,7 @@ SYSCALL_DEFINE5(perf_event_open,
> * perf_event_exit_task() that could imply).
> */
> err = -EACCES;
> - if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
> + if (!perfmon_capable() && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
> goto err_cred;
> }
>
> --
> 2.24.1
>

--

- Arnaldo