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bpf: bpf_iter_task_next: use __next_thread() rather than next_thread()

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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 <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
This commit is contained in:
Oleg Nesterov
2023-11-19 11:43:44 -08:00
committed by Alexei Starovoitov
parent 2d1618054f
commit 5a34f9dabd
1 changed files with 4 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/bpf/task_iter.c
+4 -5
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@@ -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;