Messages in this thread | | | Date | Mon, 14 Sep 2009 12:25:41 -0400 | From | Masami Hiramatsu <> | Subject | Re: [BUGFIX] kprobes: prevent re-registration of the same kprobe - take2 |
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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: > > ... > >> Hmm, if we catch the second registration here, it's too late. At >> register_kprobe(), we initialized some field of kprobe before calling >> register_aggr_kprobe(). Especially kprobe.list is cleared. >> >> And this can't check the case that 'p' is already registered on >> an aggr kprobe. > > Agreed. I thought of this case after sending out the earlier patch... > >> Thus, I think some initialization paths should be changed (kp.flag >> field is initialized too early, yearh, that's my mistake), >> and also, you will need to use get_valid_kprobe() to check the kprobe >> has not been registered. > > __get_valid_kprobe() makes the task easy. We should just prevent > re-registration whether or not the earlier probe is disabled. > > How does this patch look? > > --- > 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 == p)
Here, since __get_valid_kprobe(p) will return aggr_kprobe of 'p', you just need to check old_p != NULL.
Other parts are OK for me.
Thank you!
-- Masami Hiramatsu
Software Engineer Hitachi Computer Products (America), Inc. Software Solutions Division
e-mail: mhiramat@redhat.com
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