md: use kzalloc() when bitmap is disabled

In drivers/md/md.c get_bitmap_file() uses kmalloc() for creating a
mdu_bitmap_file_t called "file".

5769         file = kmalloc(sizeof(*file), GFP_NOIO);
5770         if (!file)
5771                 return -ENOMEM;

This structure is copied to user space at the end of the function.

5786         if (err == 0 &&
5787             copy_to_user(arg, file, sizeof(*file)))
5788                 err = -EFAULT

But if bitmap is disabled only the first byte of "file" is initialized
with zero, so it's possible to read some bytes (up to 4095) of kernel
space memory from user space. This is an information leak.

5775         /* bitmap disabled, zero the first byte and copy out */
5776         if (!mddev->bitmap_info.file)
5777                 file->pathname[0] = '\0';

Signed-off-by: Benjamin Randazzo <benjamin@randazzo.fr>
Signed-off-by: NeilBrown <neilb@suse.com>

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 0c2a4e8b873c659dbc260b2aa5484c7a5e87b176..e25f00f0138a7b4d82a5ae4f6fc7e1b6f0bb1b30 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5759,7 +5759,7 @@ static int get_bitmap_file(struct mddev *mddev, void __user * arg)
        char *ptr;
        int err;
 
-       file = kmalloc(sizeof(*file), GFP_NOIO);
+       file = kzalloc(sizeof(*file), GFP_NOIO);
        if (!file)
                return -ENOMEM;