On Thu, 5 Aug 2010, walter harms wrote:
>
>
> Namhyung Kim schrieb:
> > verify jprobe's entry point is a function entry point
> > using kallsyms' offset value.
> >
> > Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxx>
> >
> > ---
> >
> > Here comes 3rd revision of the patch. Thanks to Masami Hiramatus for suggesting
> > kallsyms_lookup_size_offset. :-)
> >
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 8f96701..1b0dbe0 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -1339,14 +1339,18 @@ int __kprobes register_jprobes(struct jprobe **jps, int num)
> > if (num <= 0)
> > return -EINVAL;
> > for (i = 0; i < num; i++) {
> > - unsigned long addr;
> > + unsigned long addr, offset;
> > jp = jps[i];
> > addr = arch_deref_entry_point(jp->entry);
> >
> > - /* Todo: Verify probepoint is a function entry point */
> > - jp->kp.pre_handler = setjmp_pre_handler;
> > - jp->kp.break_handler = longjmp_break_handler;
> > - ret = register_kprobe(&jp->kp);
> > + /* Verify probepoint is a function entry point */
> > + if (kallsyms_lookup_size_offset(addr, NULL, &offset) &&
> > + offset == 0) {
> > + jp->kp.pre_handler = setjmp_pre_handler;
> > + jp->kp.break_handler = longjmp_break_handler;
> > + ret = register_kprobe(&jp->kp);
> > + } else
> > + ret = -EINVAL;
> >
> > if (ret < 0) {
> > if (i > 0)
>
>
> I am a bit converned about this code here:
> if (kallsyms_lookup_size_offset(addr, NULL, &offset) && offset == 0)
>
> offset is set inside kallsyms_lookup_size_offset(), right ?
> but can you guarantee that the calling sequence is the same on all processors ?
> (it is not in case of functions).
&& should always be evaluated lazily from left to right. Otherwise
x != NULL && x->y == z wouldn't be safe.
julia
> perhaps it is more secure (and readable) to do:
>
> ret=kallsyms_lookup_size_offset(addr, NULL, &offset);
> if ( ret && offset == 0 )
>
> just my 2 cents,
> re,
> wh
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