Re: [PATCH] kprobes: fix race in aggregate kprobe registration

Keshavamurthy Anil S
2005-12-06T21:18:39Z

On Tue, Dec 06, 2005 at 10:47:11AM +0530, Ananth N Mavinakayanahalli wrote:
> From: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
>
> When registering multiple kprobes at the same address, we leave a small
> window where the kprobe hlist will not contain a reference to the
> registered kprobe, leading to potentially, a system crash if the
> breakpoint is hit on another processor.
>
> Patch below changes the order of hlist updation to make sure that there
> is always a reference to the kprobe at the location.

Hi Ananth,
How do you like this patch? Here the old entry
will be replace with the new entry automically.

Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>

kernel/kprobes.c | 5 +----
1 files changed, 1 insertion(+), 4 deletions(-)

Index: linux-2.6.15-rc5-mm1/kernel/kprobes.c
===================================================================
--- linux-2.6.15-rc5-mm1.orig/kernel/kprobes.c
+++ linux-2.6.15-rc5-mm1/kernel/kprobes.c
@@ -399,10 +399,7 @@ static inline void add_aggr_kprobe(struc
INIT_LIST_HEAD(&ap->list);
list_add_rcu(&p->list, &ap->list);

- INIT_HLIST_NODE(&ap->hlist);
- hlist_del_rcu(&p->hlist);
- hlist_add_head_rcu(&ap->hlist,
- &kprobe_table[hash_ptr(ap->addr, KPROBE_HASH_BITS)]);
+ hlist_replace_rcu(&p->hlist, &ap->hlist);
}

/*