[PATCH] kretprobe spinlock deadlock patch

kprobe_flush_task() possibly calls kfree function during holding
kretprobe_lock spinlock, if kfree function is probed by kretprobe that will
incur spinlock deadlock.  This patch moves kfree function out scope of
kretprobe_lock.
Signed-off-by: Nbibo, mao <bibo.mao@intel.com>
Signed-off-by: NAnanth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/kprobes.c

@@ -396,11 +396,12 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(current);
 
@@ -429,7 +430,7 @@ fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 		}
 
 		orig_ret_address = (unsigned long)ri->ret_addr;
-		recycle_rp_inst(ri);
+		recycle_rp_inst(ri, &empty_rp);
 
 		if (orig_ret_address != trampoline_address)
 			/*
@@ -444,6 +445,10 @@ fastcall void *__kprobes trampoline_handler(struct pt_regs *regs)
 
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 	return (void*)orig_ret_address;
 }
 

arch/ia64/kernel/kprobes.c

@@ -338,12 +338,13 @@ static void kretprobe_trampoline(void)
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address =
 		((struct fnptr *)kretprobe_trampoline)->ip;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(current);
 
@@ -369,7 +370,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 			ri->rp->handler(ri, regs);
 
 		orig_ret_address = (unsigned long)ri->ret_addr;
-		recycle_rp_inst(ri);
+		recycle_rp_inst(ri, &empty_rp);
 
 		if (orig_ret_address != trampoline_address)
 			/*
@@ -387,6 +388,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 	preempt_enable_no_resched();
 
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 	/*
 	 * By returning a non-zero value, we are telling
 	 * kprobe_handler() that we don't want the post_handler

arch/powerpc/kernel/kprobes.c

@@ -260,11 +260,12 @@ void kretprobe_trampoline_holder(void)
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(current);
 
@@ -290,7 +291,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 			ri->rp->handler(ri, regs);
 
 		orig_ret_address = (unsigned long)ri->ret_addr;
-		recycle_rp_inst(ri);
+		recycle_rp_inst(ri, &empty_rp);
 
 		if (orig_ret_address != trampoline_address)
 			/*
@@ -308,6 +309,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 	preempt_enable_no_resched();
 
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 	/*
 	 * By returning a non-zero value, we are telling
 	 * kprobe_handler() that we don't want the post_handler

arch/s390/kernel/kprobes.c

@@ -369,11 +369,12 @@ void __kprobes kretprobe_trampoline_holder(void)
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(current);
 
@@ -399,7 +400,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 			ri->rp->handler(ri, regs);
 
 		orig_ret_address = (unsigned long)ri->ret_addr;
-		recycle_rp_inst(ri);
+		recycle_rp_inst(ri, &empty_rp);
 
 		if (orig_ret_address != trampoline_address) {
 			/*
@@ -417,6 +418,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 	preempt_enable_no_resched();
 
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 	/*
 	 * By returning a non-zero value, we are telling
 	 * kprobe_handler() that we don't want the post_handler

arch/x86_64/kernel/kprobes.c

@@ -405,11 +405,12 @@ int __kprobes kprobe_handler(struct pt_regs *regs)
 int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 {
 	struct kretprobe_instance *ri = NULL;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags, orig_ret_address = 0;
 	unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(current);
 
@@ -435,7 +436,7 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 			ri->rp->handler(ri, regs);
 
 		orig_ret_address = (unsigned long)ri->ret_addr;
-		recycle_rp_inst(ri);
+		recycle_rp_inst(ri, &empty_rp);
 
 		if (orig_ret_address != trampoline_address)
 			/*
@@ -453,6 +454,10 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
 	preempt_enable_no_resched();
 
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 	/*
 	 * By returning a non-zero value, we are telling
 	 * kprobe_handler() that we don't want the post_handler

include/linux/kprobes.h

@@ -202,7 +202,7 @@ void unregister_kretprobe(struct kretprobe *rp);
 struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp);
 void add_rp_inst(struct kretprobe_instance *ri);
 void kprobe_flush_task(struct task_struct *tk);
-void recycle_rp_inst(struct kretprobe_instance *ri);
+void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
 #else /* CONFIG_KPROBES */
 
 #define __kprobes	/**/

kernel/kprobes.c

@@ -319,7 +319,8 @@ void __kprobes add_rp_inst(struct kretprobe_instance *ri)
 }
 
 /* Called with kretprobe_lock held */
-void __kprobes recycle_rp_inst(struct kretprobe_instance *ri)
+void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
+				struct hlist_head *head)
 {
 	/* remove rp inst off the rprobe_inst_table */
 	hlist_del(&ri->hlist);
@@ -331,7 +332,7 @@ void __kprobes recycle_rp_inst(struct kretprobe_instance *ri)
 		hlist_add_head(&ri->uflist, &ri->rp->free_instances);
 	} else
 		/* Unregistering */
-		kfree(ri);
+		hlist_add_head(&ri->hlist, head);
 }
 
 struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
@@ -348,17 +349,23 @@ struct hlist_head __kprobes *kretprobe_inst_table_head(struct task_struct *tsk)
 void __kprobes kprobe_flush_task(struct task_struct *tk)
 {
 	struct kretprobe_instance *ri;
-	struct hlist_head *head;
+	struct hlist_head *head, empty_rp;
 	struct hlist_node *node, *tmp;
 	unsigned long flags = 0;
 
+	INIT_HLIST_HEAD(&empty_rp);
 	spin_lock_irqsave(&kretprobe_lock, flags);
 	head = kretprobe_inst_table_head(tk);
 	hlist_for_each_entry_safe(ri, node, tmp, head, hlist) {
 		if (ri->task == tk)
-			recycle_rp_inst(ri);
+			recycle_rp_inst(ri, &empty_rp);
 	}
 	spin_unlock_irqrestore(&kretprobe_lock, flags);
+
+	hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) {
+		hlist_del(&ri->hlist);
+		kfree(ri);
+	}
 }
 
 static inline void free_rp_inst(struct kretprobe *rp)