Re: [PATCH bpf-next v7 2/3] bpf: clean-up bounds checking in __bpf_get_stack

["Lecomte, Arnaud" <contact@xxxxxxxxxxxxxx>]

On 05/09/2025 00:40, Song Liu wrote:
> On 9/3/25 4:40 PM, Arnaud Lecomte wrote:
> > Clean-up bounds checking for trace->nr in
> > __bpf_get_stack by limiting it only to
> > max_depth.
> >
> > Signed-off-by: Arnaud Lecomte <contact@xxxxxxxxxxxxxx>
> > Cc: Song Lui <song@xxxxxxxxxx>
>
> Typo in my name, which is "Song Liu".
>
> This looks right.
>
> Acked-by: Song Liu <song@xxxxxxxxxx>
Oops sorry !
> > ---
> >   kernel/bpf/stackmap.c | 9 +++++----
> >   1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
> > index ed707bc07173..9f3ae426ddc3 100644
> > --- a/kernel/bpf/stackmap.c
> > +++ b/kernel/bpf/stackmap.c
> > @@ -462,13 +462,15 @@ static long __bpf_get_stack(struct pt_regs 
> > *regs, struct task_struct *task,
> >       if (may_fault)
> >           rcu_read_lock(); /* need RCU for perf's callchain below */
> >   -    if (trace_in)
> > +    if (trace_in) {
> >           trace = trace_in;
> > -    else if (kernel && task)
> > +        trace->nr = min_t(u32, trace->nr, max_depth);
> > +    } else if (kernel && task) {
> >           trace = get_callchain_entry_for_task(task, max_depth);
> > -    else
> > +    } else {
> >           trace = get_perf_callchain(regs, 0, kernel, user, max_depth,
> >                          crosstask, false);
> > +    }
> >         if (unlikely(!trace) || trace->nr < skip) {
> >           if (may_fault)
> > @@ -477,7 +479,6 @@ static long __bpf_get_stack(struct pt_regs *regs, 
> > struct task_struct *task,
> >       }
> >         trace_nr = trace->nr - skip;
> > -    trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem;
> >       copy_len = trace_nr * elem_size;
> >         ips = trace->ip + skip;