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SubjectRe: [PATCH] ath9k: Fix possible data races in ath_set_channel()
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On 2020-01-11 18:15, Jia-Ju Bai wrote:
> The functions ath9k_config() and ath_ani_calibrate() may be concurrently
> executed.
>
> A variable survey->filled is accessed with holding a spinlock
> common->cc_lock, through:
> ath_ani_calibrate()
> spin_lock_irqsave(&common->cc_lock, flags);
> ath_update_survey_stats()
> ath_update_survey_nf()
> survey->filled |= SURVEY_INFO_NOISE_DBM;
>
> The identical variables sc->cur_survey->filled and
> sc->survey[pos].filled is accessed without holding this lock, through:
> ath9k_config()
> ath_chanctx_set_channel()
> ath_set_channel()
> sc->cur_survey->filled &= ~SURVEY_INFO_IN_USE;
> sc->cur_survey->filled |= SURVEY_INFO_IN_USE;
> else if (!(sc->survey[pos].filled & SURVEY_INFO_IN_USE))
> ath_update_survey_nf
> survey->filled |= SURVEY_INFO_NOISE_DBM;
>
> Thus, possible data races may occur.
>
> To fix these data races, in ath_set_channel(), these variables are
> accessed with holding the spinlock common->cc_lock.
>
> These data races are found by the runtime testing of our tool DILP-2.
>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@gmail.com>
I think a much better solution would be to stop common->ani.timer
earlier in ath_set_channel to prevent this race from occurring.

- Felix

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