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bpf: Fix a possible task gone issue with bpf_send_signal[_thread]() helpers

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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: 8b401f9ed2 ("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>
This commit is contained in:
Yonghong Song 2023-01-18 12:48:15 -08:00 committed by Alexei Starovoitov
parent 36024d023d
commit bdb7fdb0ac
1 changed files with 2 additions and 1 deletions
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3
kernel/trace/bpf_trace.c
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@ -833,6 +833,7 @@ 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)
@ -867,7 +868,7 @@ 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);