* [PATCH] drivers/md/md.c: use kzalloc() when bitmap is disabled
@ 2015-07-25 14:36 Benjamin Randazzo
2015-07-27 1:36 ` NeilBrown
0 siblings, 1 reply; 2+ messages in thread
From: Benjamin Randazzo @ 2015-07-25 14:36 UTC (permalink / raw)
To: neilb; +Cc: linux-raid, linux-kernel, Benjamin Randazzo
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>
---
drivers/md/md.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 80879dc..382bdbc 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5766,22 +5766,21 @@ 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;
err = 0;
spin_lock(&mddev->lock);
- /* bitmap disabled, zero the first byte and copy out */
- if (!mddev->bitmap_info.file)
- file->pathname[0] = '\0';
- else if ((ptr = file_path(mddev->bitmap_info.file,
- file->pathname, sizeof(file->pathname))),
- IS_ERR(ptr))
- err = PTR_ERR(ptr);
- else
- memmove(file->pathname, ptr,
- sizeof(file->pathname)-(ptr-file->pathname));
+ /* bitmap enabled */
+ if (mddev->bitmap_info.file) {
+ if ((ptr = file_path(mddev->bitmap_info.file, file->pathname,
+ sizeof(file->pathname))), IS_ERR(ptr))
+ err = PTR_ERR(ptr);
+ else
+ memmove(file->pathname, ptr,
+ sizeof(file->pathname)-(ptr-file->pathname));
+ }
spin_unlock(&mddev->lock);
if (err == 0 &&
--
2.3.6
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] drivers/md/md.c: use kzalloc() when bitmap is disabled
2015-07-25 14:36 [PATCH] drivers/md/md.c: use kzalloc() when bitmap is disabled Benjamin Randazzo
@ 2015-07-27 1:36 ` NeilBrown
0 siblings, 0 replies; 2+ messages in thread
From: NeilBrown @ 2015-07-27 1:36 UTC (permalink / raw)
To: Benjamin Randazzo; +Cc: linux-raid, linux-kernel
On Sat, 25 Jul 2015 16:36:50 +0200 Benjamin Randazzo
<benjamin@randazzo.fr> wrote:
> 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>
> ---
> drivers/md/md.c | 21 ++++++++++-----------
> 1 file changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 80879dc..382bdbc 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -5766,22 +5766,21 @@ 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;
>
> err = 0;
> spin_lock(&mddev->lock);
> - /* bitmap disabled, zero the first byte and copy out */
> - if (!mddev->bitmap_info.file)
> - file->pathname[0] = '\0';
> - else if ((ptr = file_path(mddev->bitmap_info.file,
> - file->pathname, sizeof(file->pathname))),
> - IS_ERR(ptr))
> - err = PTR_ERR(ptr);
> - else
> - memmove(file->pathname, ptr,
> - sizeof(file->pathname)-(ptr-file->pathname));
> + /* bitmap enabled */
> + if (mddev->bitmap_info.file) {
> + if ((ptr = file_path(mddev->bitmap_info.file, file->pathname,
> + sizeof(file->pathname))), IS_ERR(ptr))
> + err = PTR_ERR(ptr);
> + else
> + memmove(file->pathname, ptr,
> + sizeof(file->pathname)-(ptr-file->pathname));
> + }
> spin_unlock(&mddev->lock);
>
> if (err == 0 &&
Thanks.
I re-arranged the code a little bit more as there is no longer any
excuse for having the "ptr = file_path()" assignment inside the
condition of the 'if'.
Applied. Thanks,
NeilBrown
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