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ptp: improve max_adj check against unreasonable values
[ Upstream commit475b92f932
] Scaled PPM conversion to PPB may (on 64bit systems) result in a value larger than s32 can hold (freq/scaled_ppm is a long). This means the kernel will not correctly reject unreasonably high ->freq values (e.g. > 4294967295ppb, 281474976645 scaled PPM). The conversion is equivalent to a division by ~66 (65.536), so the value of ppb is always smaller than ppm, but not small enough to assume narrowing the type from long -> s32 is okay. Note that reasonable user space (e.g. ptp4l) will not use such high values, anyway, 4289046510ppb ~= 4.3x, so the fix is somewhat pedantic. Fixes:d39a743511
("ptp: validate the requested frequency adjustment.") Fixes:d94ba80ebb
("ptp: Added a brand new class driver for ptp clocks.") Signed-off-by: Jakub Kicinski <kuba@kernel.org> Acked-by: Richard Cochran <richardcochran@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
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2 changed files with 4 additions and 4 deletions
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@ -63,7 +63,7 @@ static void enqueue_external_timestamp(struct timestamp_event_queue *queue,
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spin_unlock_irqrestore(&queue->lock, flags);
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}
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s32 scaled_ppm_to_ppb(long ppm)
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long scaled_ppm_to_ppb(long ppm)
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{
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/*
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* The 'freq' field in the 'struct timex' is in parts per
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@ -80,7 +80,7 @@ s32 scaled_ppm_to_ppb(long ppm)
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s64 ppb = 1 + ppm;
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ppb *= 125;
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ppb >>= 13;
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return (s32) ppb;
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return (long) ppb;
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}
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EXPORT_SYMBOL(scaled_ppm_to_ppb);
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@ -138,7 +138,7 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx)
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delta = ktime_to_ns(kt);
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err = ops->adjtime(ops, delta);
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} else if (tx->modes & ADJ_FREQUENCY) {
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s32 ppb = scaled_ppm_to_ppb(tx->freq);
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long ppb = scaled_ppm_to_ppb(tx->freq);
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if (ppb > ops->max_adj || ppb < -ops->max_adj)
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return -ERANGE;
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if (ops->adjfine)
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@ -222,7 +222,7 @@ extern int ptp_clock_index(struct ptp_clock *ptp);
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* @ppm: Parts per million, but with a 16 bit binary fractional field
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*/
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extern s32 scaled_ppm_to_ppb(long ppm);
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extern long scaled_ppm_to_ppb(long ppm);
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/**
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* ptp_find_pin() - obtain the pin index of a given auxiliary function
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