Hi, are there any comments on this patch or the issue I described? I
have tested the FDGETPRM ioctl and confirmed that the struct it returns
does contain a pointer to kernel data. I also have tested my patch, and
with it applied the returned struct no longer contains a kernel pointer,
but all other fields are still present.
Thank you,
Brian Belleville
On 03/07/2018 04:02 PM, Brian Belleville wrote:
The final field of a floppy_struct is the field "name", which is a
pointer to a string in kernel memory. The kernel pointer should not be
copied to user memory. The FDGETPRM ioctl copies a floppy_struct to
user memory, including the "name" field. This pointer cannot be used
by the user, and it will leak a kernel address to user-space, which
will reveal the location of kernel code and data and undermine KASLR
protection. Instead, copy the floppy_struct except for the "name"
field.
Signed-off-by: Brian Belleville <[email protected]>
---
drivers/block/floppy.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index eae484a..4d4a422 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -3470,6 +3470,7 @@ static int fd_locked_ioctl(struct block_device *bdev,
fmode_t mode, unsigned int
(struct floppy_struct **)&outparam);
if (ret)
return ret;
+ size = offsetof(struct floppy_struct, name);
break;
case FDMSGON:
UDP->flags |= FTD_MSG;
