tree fe66d4fe237c8bb53d6a1020c536139ecc7ee446
parent 85d13c360d7c04f259d237f0b370f7cd7b32dfa9
author Benjamin Randazzo <benjamin@randazzo.fr> 1437835010 +0200
committer chrmhoffmann <chrmhoffmann@gmail.com> 1502552908 +0200

md: use kzalloc() when bitmap is disabled

commit b6878d9e03043695dbf3fa1caa6dfc09db225b16 upstream.

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';

Change-Id: I83a9f73ecdd7ffac27f547f5725f47cb9557b0a6
Signed-off-by: Benjamin Randazzo <benjamin@randazzo.fr>
Signed-off-by: NeilBrown <neilb@suse.com>
[lizf: Backported to 3.4: fix both branches]
Signed-off-by: Zefan Li <lizefan@huawei.com>