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kprobes: Free kretprobe_instance with RCU callback

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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@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/159870616685.1229682.11978742048709542226.stgit@devnote2
This commit is contained in:
Masami Hiramatsu 2020-08-29 22:02:47 +09:00 committed by Ingo Molnar
parent e03b4a084e
commit b338817807
2 changed files with 10 additions and 21 deletions
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6
include/linux/kprobes.h
View File

@ -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);

25
kernel/kprobes.c
View File

@ -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)