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Subject[PATCH] MMC: core: cap MMC card timeouts at 2 seconds.
Date
From: "Torne (Richard Coles)" <torne@google.com>

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@google.com>
---
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;
+
data->timeout_clks = card->csd.tacc_clks * mult;

/*
--
1.7.7.3


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