[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: bibo, mao <bibo.mao@intel.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/arch/i386/kernel/kprobes.c b/arch/i386/kernel/kprobes.c
index 7a97544f15a0..d98e44b16fe2 100644
--- a/arch/i386/kernel/kprobes.c
+++ b/arch/i386/kernel/kprobes.c
@@ -396,11 +396,12 @@ no_kprobe:
 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;
 }