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

[Ville Viinikka]

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 <vi...@tuxera.com>
---
 drivers/mmc/card/block.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 747c4b0..334d637 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) {
-- 
2.1.4