From: "tip-bot2 for Marco Elver" <tip-bot2@linutronix.de>
To: linux-tip-commits@vger.kernel.org
Cc: Marco Elver <elver@google.com>,
"Peter Zijlstra (Intel)" <peterz@infradead.org>,
Dmitry Vyukov <dvyukov@google.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: [tip: perf/urgent] perf: Refactor permissions check into perf_check_permission()
Date: Tue, 27 Jul 2021 13:58:55 -0000 [thread overview]
Message-ID: <162739433584.395.14125645089713310487.tip-bot2@tip-bot2> (raw)
In-Reply-To: <20210705084453.2151729-2-elver@google.com>
The following commit has been merged into the perf/urgent branch of tip:
Commit-ID: b068fc04de10fff8974f6ef32b861ad134d94ba4
Gitweb: https://git.kernel.org/tip/b068fc04de10fff8974f6ef32b861ad134d94ba4
Author: Marco Elver <elver@google.com>
AuthorDate: Mon, 05 Jul 2021 10:44:53 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 16 Jul 2021 18:46:38 +02:00
perf: Refactor permissions check into perf_check_permission()
Refactor the permission check in perf_event_open() into a helper
perf_check_permission(). This makes the permission check logic more
readable (because we no longer have a negated disjunction). Add a
comment mentioning the ptrace check also checks the uid.
No functional change intended.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Link: https://lore.kernel.org/r/20210705084453.2151729-2-elver@google.com
---
kernel/events/core.c | 58 +++++++++++++++++++++++--------------------
1 file changed, 32 insertions(+), 26 deletions(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index c13730b..1cb1f9b 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11917,6 +11917,37 @@ again:
return gctx;
}
+static bool
+perf_check_permission(struct perf_event_attr *attr, struct task_struct *task)
+{
+ unsigned int ptrace_mode = PTRACE_MODE_READ_REALCREDS;
+ bool is_capable = perfmon_capable();
+
+ if (attr->sigtrap) {
+ /*
+ * perf_event_attr::sigtrap sends signals to the other task.
+ * Require the current task to also have CAP_KILL.
+ */
+ rcu_read_lock();
+ is_capable &= ns_capable(__task_cred(task)->user_ns, CAP_KILL);
+ rcu_read_unlock();
+
+ /*
+ * If the required capabilities aren't available, checks for
+ * ptrace permissions: upgrade to ATTACH, since sending signals
+ * can effectively change the target task.
+ */
+ ptrace_mode = PTRACE_MODE_ATTACH_REALCREDS;
+ }
+
+ /*
+ * Preserve ptrace permission check for backwards compatibility. The
+ * ptrace check also includes checks that the current task and other
+ * task have matching uids, and is therefore not done here explicitly.
+ */
+ return is_capable || ptrace_may_access(task, ptrace_mode);
+}
+
/**
* sys_perf_event_open - open a performance event, associate it to a task/cpu
*
@@ -12158,43 +12189,18 @@ SYSCALL_DEFINE5(perf_event_open,
}
if (task) {
- unsigned int ptrace_mode = PTRACE_MODE_READ_REALCREDS;
- bool is_capable;
-
err = down_read_interruptible(&task->signal->exec_update_lock);
if (err)
goto err_file;
- is_capable = perfmon_capable();
- if (attr.sigtrap) {
- /*
- * perf_event_attr::sigtrap sends signals to the other
- * task. Require the current task to also have
- * CAP_KILL.
- */
- rcu_read_lock();
- is_capable &= ns_capable(__task_cred(task)->user_ns, CAP_KILL);
- rcu_read_unlock();
-
- /*
- * If the required capabilities aren't available, checks
- * for ptrace permissions: upgrade to ATTACH, since
- * sending signals can effectively change the target
- * task.
- */
- ptrace_mode = PTRACE_MODE_ATTACH_REALCREDS;
- }
-
/*
- * Preserve ptrace permission check for backwards compatibility.
- *
* We must hold exec_update_lock across this and any potential
* perf_install_in_context() call for this new event to
* serialize against exec() altering our credentials (and the
* perf_event_exit_task() that could imply).
*/
err = -EACCES;
- if (!is_capable && !ptrace_may_access(task, ptrace_mode))
+ if (!perf_check_permission(&attr, task))
goto err_cred;
}
next prev parent reply other threads:[~2021-07-27 13:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-05 8:44 [PATCH v3 1/2] perf: Fix required permissions if sigtrap is requested Marco Elver
2021-07-05 8:44 ` [PATCH v3 2/2] perf: Refactor permissions check into perf_check_permission() Marco Elver
2021-07-06 6:16 ` Dmitry Vyukov
2021-07-27 13:58 ` tip-bot2 for Marco Elver [this message]
2021-07-06 6:16 ` [PATCH v3 1/2] perf: Fix required permissions if sigtrap is requested Dmitry Vyukov
2021-07-12 10:32 ` Marco Elver
2021-07-13 9:48 ` Peter Zijlstra
2021-07-27 13:58 ` [tip: perf/urgent] " tip-bot2 for Marco Elver
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