[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 <Yanmin.zhang@intel.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/kprobes.c b/arch/x86_64/kernel/kprobes.c
index df08c43..76a28b0 100644
--- a/arch/x86_64/kernel/kprobes.c
+++ b/arch/x86_64/kernel/kprobes.c
@@ -77,9 +77,9 @@
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_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)