mmc: davinci_mmc: Prevent transmitted data size from exceeding sgm's length

No check is done on the size of the data to be transmiited. This causes
a kernel panic when this size exceeds the sg_miter's length.

Limit the number of transmitted bytes to sgm->length.

Cc: [email protected]
Fixes: ed01d21 ("mmc: davinci_mmc: Use sg_miter for PIO")
Signed-off-by: Bastien Curutchet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Ulf Hansson <[email protected]>

Author: bastien-curutchet

drivers/mmc/host/davinci_mmc.c

@@ -224,6 +224,9 @@ static void davinci_fifo_data_trans(struct mmc_davinci_host *host,
 	}
 	p = sgm->addr;
 
+	if (n > sgm->length)
+		n = sgm->length;
+
 	/* NOTE:  we never transfer more than rw_threshold bytes
 	 * to/from the fifo here; there's no I/O overlap.
 	 * This also assumes that access width( i.e. ACCWD) is 4 bytes