[RFC PATCH] panic: Add new taint flag for fault injection

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Since the function error injection framework in the fault injection
subsystem can change the function code flow forcibly, it may cause
unexpected behavior (but that is the purpose of this feature).
To identify this in the kernel oops message, add a new taint flag
for this, and set it if it is (and similar things in BPF) used.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 include/linux/panic.h    |    3 ++-
 kernel/fail_function.c   |    2 ++
 kernel/panic.c           |    1 +
 kernel/trace/bpf_trace.c |    2 ++
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/panic.h b/include/linux/panic.h
index c7759b3f2045..2b03a02d86be 100644
--- a/include/linux/panic.h
+++ b/include/linux/panic.h
@@ -69,7 +69,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
 #define TAINT_AUX			16
 #define TAINT_RANDSTRUCT		17
 #define TAINT_TEST			18
-#define TAINT_FLAGS_COUNT		19
+#define TAINT_FAULT_INJECTED		19
+#define TAINT_FLAGS_COUNT		20
 #define TAINT_FLAGS_MAX			((1UL << TAINT_FLAGS_COUNT) - 1)
 
 struct taint_flag {
diff --git a/kernel/fail_function.c b/kernel/fail_function.c
index a7ccd2930c5f..80a743f14a2c 100644
--- a/kernel/fail_function.c
+++ b/kernel/fail_function.c
@@ -9,6 +9,7 @@
 #include <linux/kprobes.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
+#include <linux/panic.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 
@@ -298,6 +299,7 @@ static ssize_t fei_write(struct file *file, const char __user *buffer,
 		fei_attr_free(attr);
 		goto out;
 	}
+	add_taint(TAINT_FAULT_INJECTED, LOCKDEP_NOW_UNRELIABLE);
 	fei_debugfs_add_attr(attr);
 	list_add_tail(&attr->list, &fei_attr_list);
 	ret = count;
diff --git a/kernel/panic.c b/kernel/panic.c
index da323209f583..e396a5fd9bb6 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -426,6 +426,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
 	[ TAINT_AUX ]			= { 'X', ' ', true },
 	[ TAINT_RANDSTRUCT ]		= { 'T', ' ', true },
 	[ TAINT_TEST ]			= { 'N', ' ', true },
+	[ TAINT_FAULT_INJECTED ]	= { 'J', ' ', false },
 };
 
 /**
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 1ed08967fb97..de0614d9796c 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -2137,6 +2137,8 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
 		goto unlock;
 
 	/* set the new array to event->tp_event and set event->prog */
+	if (prog->kprobe_override)
+		add_taint(TAINT_FAULT_INJECTED, LOCKDEP_NOW_UNRELIABLE);
 	event->prog = prog;
 	event->bpf_cookie = bpf_cookie;
 	rcu_assign_pointer(event->tp_event->prog_array, new_array);