| Message ID | 20210614222405.378030-1-kuba@kernel.org |
|---|---|
| State | New |
| Headers | show |
| Series | [net] ptp: improve max_adj check against unreasonable values | expand |
On Mon, Jun 14, 2021 at 03:24:05PM -0700, Jakub Kicinski wrote: > 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. But still important to defend against fuzzing! > Fixes: d39a743511cd ("ptp: validate the requested frequency adjustment.") > Fixes: d94ba80ebbea ("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>
Hello: This patch was applied to netdev/net.git (refs/heads/master): On Mon, 14 Jun 2021 15:24:05 -0700 you wrote: > 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. > > [...] Here is the summary with links: - [net] ptp: improve max_adj check against unreasonable values https://git.kernel.org/netdev/net/c/475b92f93216 You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/drivers/ptp/ptp_clock.c b/drivers/ptp/ptp_clock.c index 03a246e60fd9..21c4c34c52d8 100644 --- a/drivers/ptp/ptp_clock.c +++ b/drivers/ptp/ptp_clock.c @@ -63,7 +63,7 @@ static void enqueue_external_timestamp(struct timestamp_event_queue *queue, spin_unlock_irqrestore(&queue->lock, flags); } -s32 scaled_ppm_to_ppb(long ppm) +long scaled_ppm_to_ppb(long ppm) { /* * The 'freq' field in the 'struct timex' is in parts per @@ -80,7 +80,7 @@ s32 scaled_ppm_to_ppb(long ppm) s64 ppb = 1 + ppm; ppb *= 125; ppb >>= 13; - return (s32) ppb; + return (long) ppb; } EXPORT_SYMBOL(scaled_ppm_to_ppb); @@ -138,7 +138,7 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct __kernel_timex *tx) delta = ktime_to_ns(kt); err = ops->adjtime(ops, delta); } else if (tx->modes & ADJ_FREQUENCY) { - s32 ppb = scaled_ppm_to_ppb(tx->freq); + long ppb = scaled_ppm_to_ppb(tx->freq); if (ppb > ops->max_adj || ppb < -ops->max_adj) return -ERANGE; if (ops->adjfine) diff --git a/include/linux/ptp_clock_kernel.h b/include/linux/ptp_clock_kernel.h index 0d47fd33b228..51d7f1b8b32a 100644 --- a/include/linux/ptp_clock_kernel.h +++ b/include/linux/ptp_clock_kernel.h @@ -235,7 +235,7 @@ extern int ptp_clock_index(struct ptp_clock *ptp); * @ppm: Parts per million, but with a 16 bit binary fractional field */ -extern s32 scaled_ppm_to_ppb(long ppm); +extern long scaled_ppm_to_ppb(long ppm); /** * ptp_find_pin() - obtain the pin index of a given auxiliary function
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: d39a743511cd ("ptp: validate the requested frequency adjustment.") Fixes: d94ba80ebbea ("ptp: Added a brand new class driver for ptp clocks.") Signed-off-by: Jakub Kicinski <kuba@kernel.org> --- drivers/ptp/ptp_clock.c | 6 +++--- include/linux/ptp_clock_kernel.h | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-)