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

[Yafang Shao <laoar.shao@gmail.com>]

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:
-- 
2.39.1