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Date: Mon, 14 Sep 2020 17:16:13 -0000
From: "tip-bot2 for Masami Hiramatsu" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
Ingo Molnar <mingo@...nel.org>, x86 <x86@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: [tip: perf/kprobes] kprobes: Free kretprobe_instance with RCU callback
The following commit has been merged into the perf/kprobes branch of tip:
Commit-ID: b338817807538c893540e393856b79cbbdf777ea
Gitweb: https://git.kernel.org/tip/b338817807538c893540e393856b79cbbdf777ea
Author: Masami Hiramatsu <mhiramat@...nel.org>
AuthorDate: Sat, 29 Aug 2020 22:02:47 +09:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Tue, 08 Sep 2020 11:52:35 +02:00
kprobes: Free kretprobe_instance with RCU callback
Free kretprobe_instance with RCU callback instead of directly
freeing the object in the kretprobe handler context.
This will make kretprobe run safer in NMI context.
Signed-off-by: Masami Hiramatsu <mhiramat@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/159870616685.1229682.11978742048709542226.stgit@devnote2
---
include/linux/kprobes.h | 6 ++++--
kernel/kprobes.c | 25 ++++++-------------------
2 files changed, 10 insertions(+), 21 deletions(-)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 72142ae..3389067 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -156,7 +156,10 @@ struct kretprobe {
};
struct kretprobe_instance {
- struct hlist_node hlist;
+ union {
+ struct hlist_node hlist;
+ struct rcu_head rcu;
+ };
struct kretprobe *rp;
kprobe_opcode_t *ret_addr;
struct task_struct *task;
@@ -395,7 +398,6 @@ int register_kretprobes(struct kretprobe **rps, int num);
void unregister_kretprobes(struct kretprobe **rps, int num);
void kprobe_flush_task(struct task_struct *tk);
-void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
int disable_kprobe(struct kprobe *kp);
int enable_kprobe(struct kprobe *kp);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2111382..0676868 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1223,8 +1223,7 @@ void kprobes_inc_nmissed_count(struct kprobe *p)
}
NOKPROBE_SYMBOL(kprobes_inc_nmissed_count);
-void recycle_rp_inst(struct kretprobe_instance *ri,
- struct hlist_head *head)
+static void recycle_rp_inst(struct kretprobe_instance *ri)
{
struct kretprobe *rp = ri->rp;
@@ -1236,8 +1235,7 @@ void recycle_rp_inst(struct kretprobe_instance *ri,
hlist_add_head(&ri->hlist, &rp->free_instances);
raw_spin_unlock(&rp->lock);
} else
- /* Unregistering */
- hlist_add_head(&ri->hlist, head);
+ kfree_rcu(ri, rcu);
}
NOKPROBE_SYMBOL(recycle_rp_inst);
@@ -1313,7 +1311,7 @@ void kprobe_busy_end(void)
void kprobe_flush_task(struct task_struct *tk)
{
struct kretprobe_instance *ri;
- struct hlist_head *head, empty_rp;
+ struct hlist_head *head;
struct hlist_node *tmp;
unsigned long hash, flags = 0;
@@ -1323,19 +1321,14 @@ void kprobe_flush_task(struct task_struct *tk)
kprobe_busy_begin();
- INIT_HLIST_HEAD(&empty_rp);
hash = hash_ptr(tk, KPROBE_HASH_BITS);
head = &kretprobe_inst_table[hash];
kretprobe_table_lock(hash, &flags);
hlist_for_each_entry_safe(ri, tmp, head, hlist) {
if (ri->task == tk)
- recycle_rp_inst(ri, &empty_rp);
+ recycle_rp_inst(ri);
}
kretprobe_table_unlock(hash, &flags);
- hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
- hlist_del(&ri->hlist);
- kfree(ri);
- }
kprobe_busy_end();
}
@@ -1936,13 +1929,12 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
void *frame_pointer)
{
struct kretprobe_instance *ri = NULL, *last = NULL;
- struct hlist_head *head, empty_rp;
+ struct hlist_head *head;
struct hlist_node *tmp;
unsigned long flags;
kprobe_opcode_t *correct_ret_addr = NULL;
bool skipped = false;
- INIT_HLIST_HEAD(&empty_rp);
kretprobe_hash_lock(current, &head, &flags);
/*
@@ -2011,7 +2003,7 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
__this_cpu_write(current_kprobe, prev);
}
- recycle_rp_inst(ri, &empty_rp);
+ recycle_rp_inst(ri);
if (ri == last)
break;
@@ -2019,11 +2011,6 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs,
kretprobe_hash_unlock(current, &flags);
- hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
- hlist_del(&ri->hlist);
- kfree(ri);
- }
-
return (unsigned long)correct_ret_addr;
}
NOKPROBE_SYMBOL(__kretprobe_trampoline_handler)
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