mmc: Avoid buffer overrun in mmc_startup()
If the CSD register contains a reserved value (4 - 7) in bits 0:2 of the
TRAN_SPEED field, a buffer overrun occurs. Resize the mapping table.
According to the original report
https://lore.kernel.org/u-boot/20180826231332.2491-11-erosca@de.adit-jv.com/
reserved values have been observed resulting in a buffer overrun.
Reported-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Fixes: 272cc70b211e ("Add MMC Framework")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index d96db7a..00f4964 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1570,13 +1570,20 @@
return 0;
}
#endif
-/* frequency bases */
-/* divided by 10 to be nice to platforms without floating point */
+/*
+ * TRAN_SPEED bits 0:2 encode the frequency unit:
+ * 0 = 100KHz, 1 = 1MHz, 2 = 10MHz, 3 = 100MHz, values 4 - 7 are reserved.
+ * The values in fbase[] are divided by 10 to avoid floats in multiplier[].
+ */
static const int fbase[] = {
10000,
100000,
1000000,
10000000,
+ 0, /* reserved */
+ 0, /* reserved */
+ 0, /* reserved */
+ 0, /* reserved */
};
/* Multiplier values for TRAN_SPEED. Multiplied by 10 to be nice
@@ -2560,6 +2567,8 @@
mult = multipliers[((cmd.response[0] >> 3) & 0xf)];
mmc->legacy_speed = freq * mult;
+ if (!mmc->legacy_speed)
+ log_debug("TRAN_SPEED: reserved value");
mmc_select_mode(mmc, MMC_LEGACY);
mmc->dsr_imp = ((cmd.response[1] >> 12) & 0x1);