Re: [PATCH bpf-next 1/3] bpf: Fix an issue due to uninitialized bpf_iter_task

[Yonghong Song <yonghong.song@linux.dev>]

On 2/8/24 1:41 AM, Chuyi Zhou 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@gmail.com>
>> Cc: Chuyi Zhou <zhouchuyi@bytedance.com>
>> ---
>>   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.

Sorry, I missed this during reviewing commit ac8148d957f5043.
Your change LGTM.

Acked-by: Yonghong Song <yonghong.song@linux.dev>