On 4/2/24 6:58 PM, Andrii Nakryiko wrote:
On Mon, Apr 1, 2024 at 12:16 PM Kui-Feng Lee <thinker.li@xxxxxxxxx> wrote:rethook_find_ret_addr() prints a warning message and returns 0 when the target task is running and not the "current" task to prevent returning an incorrect return address. However, this check is incomplete as the target task can still transition to the running state when finding the return address, although it is safe with RCU. The issue we encounter is that the kernel frequently prints warning messages when BPF profiling programs call to bpf_get_task_stack() on running tasks. The callers should be aware and willing to take the risk of receiving an incorrect return address from a task that is currently running other than the "current" one. A warning is not needed here as the callers are intent on it. Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx> --- kernel/trace/rethook.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c index fa03094e9e69..4297a132a7ae 100644 --- a/kernel/trace/rethook.c +++ b/kernel/trace/rethook.c @@ -248,7 +248,7 @@ unsigned long rethook_find_ret_addr(struct task_struct *tsk, unsigned long frame if (WARN_ON_ONCE(!cur)) return 0; - if (WARN_ON_ONCE(tsk != current && task_is_running(tsk))) + if (tsk != current && task_is_running(tsk)) return 0;This should probably go through Masami's tree, but the change makes sense to me, given this is an expected condition. Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Masami, I assume you'll pick this up? Thanks, Daniel
