Messages in this thread Patch in this message | | | Date | Tue, 15 Sep 2009 10:43:07 +0530 | From | Ananth N Mavinakayanahalli <> | Subject | Re: [BUGFIX] kprobes: prevent re-registration of the same kprobe - take2 |
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On Mon, Sep 14, 2009 at 12:25:41PM -0400, Masami Hiramatsu wrote: > Ananth N Mavinakayanahalli wrote: >> On Sun, Sep 13, 2009 at 09:47:39PM -0400, Masami Hiramatsu wrote: >>> Ananth N Mavinakayanahalli wrote: >>>> On Fri, Sep 11, 2009 at 05:12:54AM +0200, Frederic Weisbecker wrote: >>>>> On Thu, Sep 10, 2009 at 07:53:30PM -0400, Masami Hiramatsu wrote:
...
>> +static inline int check_kprobe_rereg(struct kprobe *p) >> +{ >> + int ret = 0; >> + struct kprobe *old_p; >> + >> + mutex_lock(&kprobe_mutex); >> + old_p = __get_valid_kprobe(p); >> + if (old_p == p) > > Here, since __get_valid_kprobe(p) will return aggr_kprobe of 'p', > you just need to check old_p != NULL.
Right!
--- Prevent re-registration of the same kprobe. This situation, though unlikely, needs to be flagged since it can lead to a system crash if its not handled.
The core change itself is small, but the helper routine needed to be moved around a bit; hence the diffstat.
Signed-off-by: Ananth N Mavinakayanahalli<ananth@in.ibm.com> --- kernel/kprobes.c | 58 ++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 38 insertions(+), 20 deletions(-)
Index: linux-2.6.31/kernel/kprobes.c =================================================================== --- linux-2.6.31.orig/kernel/kprobes.c +++ linux-2.6.31/kernel/kprobes.c @@ -681,6 +681,40 @@ static kprobe_opcode_t __kprobes *kprobe return (kprobe_opcode_t *)(((char *)addr) + p->offset); } +/* Check passed kprobe is valid and return kprobe in kprobe_table. */ +static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p) +{ + struct kprobe *old_p, *list_p; + + old_p = get_kprobe(p->addr); + if (unlikely(!old_p)) + return NULL; + + if (p != old_p) { + list_for_each_entry_rcu(list_p, &old_p->list, list) + if (list_p == p) + /* kprobe p is a valid probe */ + goto valid; + return NULL; + } +valid: + return old_p; +} + +/* Return error if the kprobe is being re-registered */ +static inline int check_kprobe_rereg(struct kprobe *p) +{ + int ret = 0; + struct kprobe *old_p; + + mutex_lock(&kprobe_mutex); + old_p = __get_valid_kprobe(p); + if (old_p) + ret = -EINVAL; + mutex_unlock(&kprobe_mutex); + return ret; +} + int __kprobes register_kprobe(struct kprobe *p) { int ret = 0; @@ -693,6 +727,10 @@ int __kprobes register_kprobe(struct kpr return -EINVAL; p->addr = addr; + ret = check_kprobe_rereg(p); + if (ret) + return ret; + preempt_disable(); if (!kernel_text_address((unsigned long) p->addr) || in_kprobes_functions((unsigned long) p->addr)) { @@ -762,26 +800,6 @@ out: } EXPORT_SYMBOL_GPL(register_kprobe); -/* Check passed kprobe is valid and return kprobe in kprobe_table. */ -static struct kprobe * __kprobes __get_valid_kprobe(struct kprobe *p) -{ - struct kprobe *old_p, *list_p; - - old_p = get_kprobe(p->addr); - if (unlikely(!old_p)) - return NULL; - - if (p != old_p) { - list_for_each_entry_rcu(list_p, &old_p->list, list) - if (list_p == p) - /* kprobe p is a valid probe */ - goto valid; - return NULL; - } -valid: - return old_p; -} - /* * Unregister a kprobe without a scheduler synchronization. */
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