On Mon, 2012-05-28 at 18:31 +0100, Torne (Richard Coles) 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. Needs a 'Signed-off-by'. > --- > 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; We clearly need to guard against overflow here, and this is the correct way to clamp the multiplication. I can't speak as to whether 2 seconds is the right limit. Ben. > data->timeout_clks = card->csd.tacc_clks * mult; > > /* -- Ben Hutchings Teamwork is essential - it allows you to blame someone else.
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