linux-kernel - [PATCH V3] MMC: core: cap MMC card timeouts at UINT

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Message-Id: <1338556815-26487-1-git-send-email-torne@google.com>
Date:	Fri,  1 Jun 2012 14:20:15 +0100
From:	"Torne (Richard Coles)" <torne@...gle.com>
To:	cjb@...top.org
Cc:	linus.walleij@...aro.org, jh80.chung@...sung.com,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
	ben@...adent.org.uk, "Torne (Richard Coles)" <torne@...gle.com>
Subject: [PATCH V3] MMC: core: cap MMC card timeouts at UINT_MAX

From: "Torne (Richard Coles)" <torne@...gle.com>

MMC CSD info can specify very large, ridiculous timeouts, big enough to
overflow timeout_ns. 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 UINT_MAX.  Cards specifying
longer timeouts are almost certainly insane, and host controllers
generally cannot support timeouts that long in any case.

Signed-off-by: Torne (Richard Coles) <torne@...gle.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..74ec3d4 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
+	 * UINT_MAX to avoid the overflow; host controllers cannot generally
+	 * generate timeouts that long anyway.
+	 */
+	if (card->csd.tacc_ns <= UINT_MAX / mult)
+		data->timeout_ns = card->csd.tacc_ns * mult;
+	else
+		data->timeout_ns = UINT_MAX;
+
 	data->timeout_clks = card->csd.tacc_clks * mult;
 
 	/*
-- 
1.7.7.3

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