From: Oleg Nesterov Date: Tue, 14 Nov 2023 16:32:37 +0000 (+0100) Subject: bpf: bpf_iter_task_next: use __next_thread() rather than next_thread() X-Git-Tag: v6.8-rc1~131^2~289^2~2^2~1 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=5a34f9dabd9aa567e2d37e1aa27a67f80acfaa1c;p=linux-block.git bpf: bpf_iter_task_next: use __next_thread() rather than next_thread() Lockless use of next_thread() should be avoided, kernel/bpf/task_iter.c is the last user and the usage is wrong. bpf_iter_task_next() can loop forever, "kit->pos == kit->task" can never happen if kit->pos execs. Change this code to use __next_thread(). With or without this change the usage of kit->pos/task and next_task() doesn't look nice, see the next patch. Signed-off-by: Oleg Nesterov Acked-by: Yonghong Song Link: https://lore.kernel.org/r/20231114163237.GA897@redhat.com Signed-off-by: Alexei Starovoitov --- diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 51ae15e2b290..d42e08d0d0b7 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -1015,12 +1015,11 @@ __bpf_kfunc struct task_struct *bpf_iter_task_next(struct bpf_iter_task *it) if (flags == BPF_TASK_ITER_ALL_PROCS) goto get_next_task; - kit->pos = next_thread(kit->pos); - if (kit->pos == kit->task) { - if (flags == BPF_TASK_ITER_PROC_THREADS) { - kit->pos = NULL; + kit->pos = __next_thread(kit->pos); + if (!kit->pos) { + if (flags == BPF_TASK_ITER_PROC_THREADS) return pos; - } + kit->pos = kit->task; } else return pos;