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Date: Wed, 3 Jan 2018 02:40:48 +0100
From: Jessica Yu <jeyu@...nel.org>
To: Masami Hiramatsu <mhiramat@...nel.org>,
Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
"David S . Miller" <davem@...emloft.net>,
Ingo Molnar <mingo@...nel.org>
Cc: Petr Mladek <pmladek@...e.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Joe Lawrence <joe.lawrence@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Miroslav Benes <mbenes@...e.cz>,
Steven Rostedt <rostedt@...dmis.org>,
live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
Jessica Yu <jeyu@...nel.org>
Subject: [PATCH v3 2/2] kprobes: propagate error from disarm_kprobe_ftrace()
Improve error handling when disarming ftrace-based kprobes. Like with
arm_kprobe_ftrace(), propagate any errors from disarm_kprobe_ftrace() so
that we do not disable/unregister kprobes that are still armed. In other
words, unregister_kprobe() and disable_kprobe() should not report success
if the kprobe could not be disarmed.
disarm_all_kprobes() keeps its current behavior and attempts to
disarm all kprobes. It returns the last encountered error and gives a
warning if not all probes could be disarmed.
This patch is based on Petr Mladek's original patchset (patches 2 and 3)
back in 2015, which improved kprobes error handling, found here:
https://lkml.org/lkml/2015/2/26/452
However, further work on this had been paused since then and the patches
were not upstreamed.
Based-on-patches-by: Petr Mladek <pmladek@...e.com>
Acked-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Jessica Yu <jeyu@...nel.org>
---
kernel/kprobes.c | 76 +++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 51 insertions(+), 25 deletions(-)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index ae6b6fe79de3..10b7139a141a 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1017,23 +1017,27 @@ static int arm_kprobe_ftrace(struct kprobe *p)
}
/* Caller must lock kprobe_mutex */
-static void disarm_kprobe_ftrace(struct kprobe *p)
+static int disarm_kprobe_ftrace(struct kprobe *p)
{
- int ret;
+ int ret = 0;
- kprobe_ftrace_enabled--;
- if (kprobe_ftrace_enabled == 0) {
+ if (kprobe_ftrace_enabled == 1) {
ret = unregister_ftrace_function(&kprobe_ftrace_ops);
- WARN(ret < 0, "Failed to init kprobe-ftrace (%d)\n", ret);
+ if (WARN(ret < 0, "Failed to unregister kprobe-ftrace (%d)\n", ret))
+ return ret;
}
+
+ kprobe_ftrace_enabled--;
+
ret = ftrace_set_filter_ip(&kprobe_ftrace_ops,
(unsigned long)p->addr, 1, 0);
WARN(ret < 0, "Failed to disarm kprobe-ftrace at %p (%d)\n", p->addr, ret);
+ return ret;
}
#else /* !CONFIG_KPROBES_ON_FTRACE */
#define prepare_kprobe(p) arch_prepare_kprobe(p)
#define arm_kprobe_ftrace(p) (0)
-#define disarm_kprobe_ftrace(p) do {} while (0)
+#define disarm_kprobe_ftrace(p) (0)
#endif
/* Arm a kprobe with text_mutex */
@@ -1052,18 +1056,18 @@ static int arm_kprobe(struct kprobe *kp)
}
/* Disarm a kprobe with text_mutex */
-static void disarm_kprobe(struct kprobe *kp, bool reopt)
+static int disarm_kprobe(struct kprobe *kp, bool reopt)
{
- if (unlikely(kprobe_ftrace(kp))) {
- disarm_kprobe_ftrace(kp);
- return;
- }
+ if (unlikely(kprobe_ftrace(kp)))
+ return disarm_kprobe_ftrace(kp);
cpus_read_lock();
mutex_lock(&text_mutex);
__disarm_kprobe(kp, reopt);
mutex_unlock(&text_mutex);
cpus_read_unlock();
+
+ return 0;
}
/*
@@ -1656,11 +1660,12 @@ static int aggr_kprobe_disabled(struct kprobe *ap)
static struct kprobe *__disable_kprobe(struct kprobe *p)
{
struct kprobe *orig_p;
+ int ret;
/* Get an original kprobe for return */
orig_p = __get_valid_kprobe(p);
if (unlikely(orig_p == NULL))
- return NULL;
+ return ERR_PTR(-EINVAL);
if (!kprobe_disabled(p)) {
/* Disable probe if it is a child probe */
@@ -1674,8 +1679,13 @@ static struct kprobe *__disable_kprobe(struct kprobe *p)
* should have already been disarmed, so
* skip unneed disarming process.
*/
- if (!kprobes_all_disarmed)
- disarm_kprobe(orig_p, true);
+ if (!kprobes_all_disarmed) {
+ ret = disarm_kprobe(orig_p, true);
+ if (ret) {
+ p->flags &= ~KPROBE_FLAG_DISABLED;
+ return ERR_PTR(ret);
+ }
+ }
orig_p->flags |= KPROBE_FLAG_DISABLED;
}
}
@@ -1692,8 +1702,8 @@ static int __unregister_kprobe_top(struct kprobe *p)
/* Disable kprobe. This will disarm it if needed. */
ap = __disable_kprobe(p);
- if (ap == NULL)
- return -EINVAL;
+ if (IS_ERR(ap))
+ return PTR_ERR(ap);
if (ap == p)
/*
@@ -2126,12 +2136,14 @@ static void kill_kprobe(struct kprobe *p)
int disable_kprobe(struct kprobe *kp)
{
int ret = 0;
+ struct kprobe *p;
mutex_lock(&kprobe_mutex);
/* Disable this kprobe */
- if (__disable_kprobe(kp) == NULL)
- ret = -EINVAL;
+ p = __disable_kprobe(kp);
+ if (IS_ERR(p))
+ ret = PTR_ERR(p);
mutex_unlock(&kprobe_mutex);
return ret;
@@ -2638,34 +2650,48 @@ static int arm_all_kprobes(void)
return ret;
}
-static void disarm_all_kprobes(void)
+static int disarm_all_kprobes(void)
{
struct hlist_head *head;
struct kprobe *p;
- unsigned int i;
+ unsigned int i, errors = 0;
+ int err, ret = 0;
mutex_lock(&kprobe_mutex);
/* If kprobes are already disarmed, just return */
if (kprobes_all_disarmed) {
mutex_unlock(&kprobe_mutex);
- return;
+ return 0;
}
kprobes_all_disarmed = true;
- printk(KERN_INFO "Kprobes globally disabled\n");
for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
head = &kprobe_table[i];
+ /* Disarm all kprobes on a best-effort basis */
hlist_for_each_entry_rcu(p, head, hlist) {
- if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p))
- disarm_kprobe(p, false);
+ if (!arch_trampoline_kprobe(p) && !kprobe_disabled(p)) {
+ err = disarm_kprobe(p, false);
+ if (err) {
+ errors++;
+ ret = err;
+ }
+ }
}
}
+
+ if (errors)
+ pr_warn("Kprobes globally disabled, but failed to disarm %d probes\n", errors);
+ else
+ pr_info("Kprobes globally disabled\n");
+
mutex_unlock(&kprobe_mutex);
/* Wait for disarming all kprobes by optimizer */
wait_for_kprobe_optimizer();
+
+ return ret;
}
/*
@@ -2708,7 +2734,7 @@ static ssize_t write_enabled_file_bool(struct file *file,
case 'n':
case 'N':
case '0':
- disarm_all_kprobes();
+ ret = disarm_all_kprobes();
break;
default:
return -EINVAL;
--
2.13.6
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