From 2dd960d66bc12b6b206e63104636514e5da0ddb7 Mon Sep 17 00:00:00 2001 From: "Zhang, Yanmin" Date: Fri, 30 Sep 2005 11:59:20 -0700 Subject: [PATCH] [PATCH] utilization of kprobe_mutex is incorrect on x86_64 The up()/down() orders are incorrect in arch/x86_64/kprobes.c file. kprobe_mutext is used to protect the free kprobe instruction slot list. arch_prepare_kprobe applies for a slot from the free list, and arch_remove_kprobe returns a slot to the free list. The incorrect up()/down() orders to operate on kprobe_mutex fail to protect the free list. If 2 threads try to get/return kprobe instruction slot at the same time, the free slot list might be broken, or a free slot might be applied by 2 threads. Signed-off-by: Zhang Yanmin Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/kprobes.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c index df08c43276a0..76a28b007be9 100644 --- a/arch/x86_64/kernel/kprobes.c +++ b/arch/x86_64/kernel/kprobes.c @@ -77,9 +77,9 @@ static inline int is_IF_modifier(kprobe_opcode_t *insn) int __kprobes arch_prepare_kprobe(struct kprobe *p) { /* insn: must be on special executable page on x86_64. */ - up(&kprobe_mutex); - p->ainsn.insn = get_insn_slot(); down(&kprobe_mutex); + p->ainsn.insn = get_insn_slot(); + up(&kprobe_mutex); if (!p->ainsn.insn) { return -ENOMEM; } @@ -231,9 +231,9 @@ void __kprobes arch_disarm_kprobe(struct kprobe *p) void __kprobes arch_remove_kprobe(struct kprobe *p) { - up(&kprobe_mutex); - free_insn_slot(p->ainsn.insn); down(&kprobe_mutex); + free_insn_slot(p->ainsn.insn); + up(&kprobe_mutex); } static inline void save_previous_kprobe(void) -- 2.20.1