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    SubjectRe: [PATCH] b43legacy: Fix a sleep-in-atomic bug in b43legacy_op_bss_info_changed
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    On 31-05-17 12:26, Kalle Valo wrote:
    > Jia-Ju Bai <baijiaju1990@163.com> writes:
    >
    >> The driver may sleep under a spin lock, and the function call path is:
    >> b43legacy_op_bss_info_changed (acquire the lock by spin_lock_irqsave)
    >> b43legacy_synchronize_irq
    >> synchronize_irq --> may sleep
    >>
    >> To fix it, the lock is released before b43legacy_synchronize_irq, and the
    >> lock is acquired again after this function.
    >>
    >> Signed-off-by: Jia-Ju Bai <baijiaju1990@163.com>
    >> ---
    >> drivers/net/wireless/broadcom/b43legacy/main.c | 2 ++
    >> 1 file changed, 2 insertions(+)
    >>
    >> diff --git a/drivers/net/wireless/broadcom/b43legacy/main.c b/drivers/net/wireless/broadcom/b43legacy/main.c
    >> index f1e3dad..31ead21 100644
    >> --- a/drivers/net/wireless/broadcom/b43legacy/main.c
    >> +++ b/drivers/net/wireless/broadcom/b43legacy/main.c
    >> @@ -2859,7 +2859,9 @@ static void b43legacy_op_bss_info_changed(struct ieee80211_hw *hw,
    >> b43legacy_write32(dev, B43legacy_MMIO_GEN_IRQ_MASK, 0);
    >>
    >> if (changed & BSS_CHANGED_BSSID) {
    >> + spin_unlock_irqrestore(&wl->irq_lock, flags);
    >> b43legacy_synchronize_irq(dev);
    >> + spin_lock_irqsave(&wl->irq_lock, flags);
    >
    > To me this looks like a fragile workaround and not a real fix. You can
    > easily add new race conditions with releasing the lock like this.

    Hi Jia-Ju,

    Agree with Kalle as I was about to say the same thing. You really need
    to determine what is protected by the irq_lock. Here you are using the
    lock because you are about to change wl->bssid a bit further down. Did
    not check the entire function but it seems the lock perimeter is too wide.

    Regards,
    Arend

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