[Patch] block: do not leak info to user-space

[Cong Wang]

From: Cong Wang <amwang@xxxxxxxxxx>

There is a hole in struct hd_geometry, so we have to
zero the struct on stack before copying it to user-space.

Cc: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Cong Wang <amwang@xxxxxxxxxx>

---
diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index 7c668c8..7e5d474 100644
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -59,6 +59,7 @@ static int compat_hdio_getgeo(struct gendisk *disk, struct block_device *bdev,
 	if (!disk->fops->getgeo)
 		return -ENOTTY;
 
+	memset(&geo, 0, sizeof(geo));
 	/*
 	 * We need to set the startsect first, the driver may
 	 * want to override it.
--
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