On 31 May 2012 11:00, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: > Hi Richard, > > On 29 May 2012 17:02, Torne (Richard Coles) <torne@xxxxxxxxxx> wrote: >> From: "Torne (Richard Coles)" <torne@xxxxxxxxxx> >> >> MMC CSD info can specify very large, ridiculous timeouts, big enough to >> overflow timeout_ns on 32-bit machines. This can result in the card >> timing out on every operation because the wrapped timeout value is far >> too small. >> >> Fix the overflow by capping the result at 2 seconds. Cards specifying >> longer timeouts are almost certainly insane, and host controllers >> generally cannot support timeouts that long in any case. >> >> 2 seconds should be plenty of time for any card to actually function; >> the timeout calculation code is already using 1 second as a "worst case" >> timeout for cards running in SPI mode. >> >> Signed-off-by: Torne (Richard Coles) <torne@xxxxxxxxxx> >> --- >> drivers/mmc/core/core.c | 11 ++++++++++- >> 1 files changed, 10 insertions(+), 1 deletions(-) >> >> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c >> index 0b6141d..3b4a9fc 100644 >> --- a/drivers/mmc/core/core.c >> +++ b/drivers/mmc/core/core.c >> @@ -512,7 +512,16 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card) >> if (data->flags & MMC_DATA_WRITE) >> mult <<= card->csd.r2w_factor; >> >> - data->timeout_ns = card->csd.tacc_ns * mult; >> + /* >> + * The timeout in nanoseconds may overflow with some cards. Cap it at >> + * two seconds both to avoid the overflow and also because host >> + * controllers cannot generally generate timeouts that long anyway. >> + */ >> + if (card->csd.tacc_ns <= (2 * NSEC_PER_SEC) / mult) >> + data->timeout_ns = card->csd.tacc_ns * mult; >> + else >> + data->timeout_ns = 2 * NSEC_PER_SEC; >> + > > The above looks OK to me, although if doing this for tacc_ns we might > want to do this for tacc_clks as well. Could we include that is this > patch as well? timeout_clks can't overflow, that I can see: the highest possible value for tacc_clks is 25500 (it's an 8 bit field specified in 100-clock increments) and the highest mult is 12800 (r2w_factor only goes up to 128). This only makes 0x13747800 :) >> data->timeout_clks = card->csd.tacc_clks * mult; >> >> /* >> -- >> 1.7.7.3 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-mmc" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > Kind regards > Ulf Hansson -- Torne (Richard Coles) torne@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
