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authorLinus Torvalds <torvalds@linux-foundation.org>2021-08-08 21:46:13 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-08-08 21:46:13 +0300
commit74eedeba459d878484634cbfd5d1c2fbaf7178b9 (patch)
treeb1d76c95696563d958ffb53d3eeb29905beef0bf /kernel
parent66745863ecdec7abbfc3325c2d917eecb739c069 (diff)
parentacade6379930dfa7987f4bd9b26d1a701cc1b542 (diff)
downloadlinux-74eedeba459d878484634cbfd5d1c2fbaf7178b9.tar.xz
Merge tag 'perf-urgent-2021-08-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Thomas Gleixner: "A set of perf fixes: - Correct the permission checks for perf event which send SIGTRAP to a different process and clean up that code to be more readable. - Prevent an out of bound MSR access in the x86 perf code which happened due to an incomplete limiting to the actually available hardware counters. - Prevent access to the AMD64_EVENTSEL_HOSTONLY bit when running inside a guest. - Handle small core counter re-enabling correctly by issuing an ACK right before reenabling it to prevent a stale PEBS record being kept around" * tag 'perf-urgent-2021-08-08' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: perf/x86/intel: Apply mid ACK for small core perf/x86/amd: Don't touch the AMD64_EVENTSEL_HOSTONLY bit inside the guest perf/x86: Fix out of bound MSR access perf: Refactor permissions check into perf_check_permission() perf: Fix required permissions if sigtrap is requested
Diffstat (limited to 'kernel')
-rw-r--r--kernel/events/core.c35
1 files changed, 32 insertions, 3 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 464917096e73..1cb1f9b8392e 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
*
@@ -12163,15 +12194,13 @@ SYSCALL_DEFINE5(perf_event_open,
goto err_file;
/*
- * 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 (!perfmon_capable() && !ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS))
+ if (!perf_check_permission(&attr, task))
goto err_cred;
}