On Thu, Feb 8, 2024 at 5:41 PM Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx> wrote:
>
> Hello,
>
> 在 2024/2/8 17:09, Yafang Shao 写道:
> > Failure to initialize it->pos, coupled with the presence of an invalid
> > value in the flags variable, can lead to it->pos referencing an invalid
> > task, potentially resulting in a kernel panic. To mitigate this risk, it's
> > crucial to ensure proper initialization of it->pos to 0.
> >
> > Fixes: c68a78ffe2cb ("bpf: Introduce task open coded iterator kfuncs")
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > Cc: Chuyi Zhou <zhouchuyi@xxxxxxxxxxxxx>
> > ---
> > kernel/bpf/task_iter.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c
> > index e5c3500443c6..ec4e97c61eef 100644
> > --- a/kernel/bpf/task_iter.c
> > +++ b/kernel/bpf/task_iter.c
> > @@ -978,6 +978,8 @@ __bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it,
> > BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) !=
> > __alignof__(struct bpf_iter_task));
> >
> > + kit->pos = NULL;
> > +
> > switch (flags) {
> > case BPF_TASK_ITER_ALL_THREADS:
> > case BPF_TASK_ITER_ALL_PROCS:
>
> LGTM.
>
> Actually commit c68a78ffe2c ("bpf: Introduce task open coded iterator
> kfuncs") initialize it->pos to NULL. But it seems the following commit
> ac8148d957f5043 ("bpf: bpf_iter_task_next: use next_task(kit->task)
> rather than next_task(kit->pos)") drops this initialization.
>
Thanks for your quick response. Will update the fixes tag in the next version.
--
Regards
Yafang
