Patch "md: use kzalloc() when bitmap is disabled" has been added to the 3.10-stable tree

This is a note to let you know that I've just added the patch titled

md: use kzalloc() when bitmap is disabled

to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
md-use-kzalloc-when-bitmap-is-disabled.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Benjamin Randazzo <[email protected]>
Date: Sat, 25 Jul 2015 16:36:50 +0200
Subject: md: use kzalloc() when bitmap is disabled

From: Benjamin Randazzo <[email protected]>

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';

---
 drivers/md/md.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -5628,9 +5628,9 @@ static int get_bitmap_file(struct mddev
 	int err = -ENOMEM;
 
 	if (md_allow_write(mddev))
-		file = kmalloc(sizeof(*file), GFP_NOIO);
+		file = kzalloc(sizeof(*file), GFP_NOIO);
 	else
-		file = kmalloc(sizeof(*file), GFP_KERNEL);
+		file = kzalloc(sizeof(*file), GFP_KERNEL);
 
 	if (!file)
 		goto out;

Patches currently in stable-queue which might be from [email protected] are

queue-3.10/md-use-kzalloc-when-bitmap-is-disabled.patch