mmc: block: fix free of uninitialized 'idata->buf'

Set 'idata->buf' to NULL so that it never gets returned without
initialization. This fixes a bug where mmc_blk_ioctl_cmd() would
free both 'idata' and 'idata->buf' but 'idata->buf' was returned
uninitialized.

Fixes: 1ff8950c0433 ("mmc: block: change to use kmalloc when copy data from userspace")
Signed-off-by: Ville Viinikka <ville@tuxera.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index e62fde3ac431..c13ba2ab19d6 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -355,8 +355,10 @@ static struct mmc_blk_ioc_data *mmc_blk_ioctl_copy_from_user(
                 goto idata_err;
         }
 
-        if (!idata->buf_bytes)
+        if (!idata->buf_bytes) {
+                idata->buf = NULL;
                 return idata;
+        }
 
         idata->buf = kmalloc(idata->buf_bytes, GFP_KERNEL);
         if (!idata->buf) {