From: Yonghong Song yhs@fb.com
[ Upstream commit bdb7fdb0aca8b96cef9995d3a57e251c2289322f ]
In current bpf_send_signal() and bpf_send_signal_thread() helper implementation, irq_work is used to handle nmi context. Hao Sun reported in [1] that the current task at the entry of the helper might be gone during irq_work callback processing. To fix the issue, a reference is acquired for the current task before enqueuing into the irq_work so that the queued task is still available during irq_work callback processing.
[1] https://lore.kernel.org/bpf/20230109074425.12556-1-sunhao.th@gmail.com/
Fixes: 8b401f9ed244 ("bpf: implement bpf_send_signal() helper") Tested-by: Hao Sun sunhao.th@gmail.com Reported-by: Hao Sun sunhao.th@gmail.com Signed-off-by: Yonghong Song yhs@fb.com Link: https://lore.kernel.org/r/20230118204815.3331855-1-yhs@fb.com Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/bpf_trace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index ab4f51716645..94e51d36fb49 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -1055,6 +1055,7 @@ static void do_bpf_send_signal(struct irq_work *entry)
work = container_of(entry, struct send_signal_irq_work, irq_work); group_send_sig_info(work->sig, SEND_SIG_PRIV, work->task, work->type); + put_task_struct(work->task); }
static int bpf_send_signal_common(u32 sig, enum pid_type type) @@ -1091,7 +1092,7 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type) * to the irq_work. The current task may change when queued * irq works get executed. */ - work->task = current; + work->task = get_task_struct(current); work->sig = sig; work->type = type; irq_work_queue(&work->irq_work);