On Wed, 03 Jan 2007 17:46:00 -0600
Eric Sandeen <[EMAIL PROTECTED]> wrote:
> Take 2... all in one file. I suppose I really did know better than
> to create that new header. ;-)
>
> Better?
>
> ---
>
> CVE-2006-5753 is for a case where an inode can be marked bad, switching
> the ops to bad_inode_ops, which are all connected as:
>
> static int return_EIO(void)
> {
> return -EIO;
> }
>
> #define EIO_ERROR ((void *) (return_EIO))
>
> static struct inode_operations bad_inode_ops =
> {
> .create = bad_inode_create
> ...etc...
>
> The problem here is that the void cast causes return types to not be
> promoted, and for ops such as listxattr which expect more than 32 bits of
> return value, the 32-bit -EIO is interpreted as a large positive 64-bit
> number, i.e. 0x00000000fffffffa instead of 0xfffffffa.
>
> This goes particularly badly when the return value is taken as a number of
> bytes to copy into, say, a user's buffer for example...
>
> I originally had coded up the fix by creating a return_EIO_<TYPE> macro
> for each return type, like this:
>
> static int return_EIO_int(void)
> {
> return -EIO;
> }
> #define EIO_ERROR_INT ((void *) (return_EIO_int))
>
> static struct inode_operations bad_inode_ops =
> {
> .create = EIO_ERROR_INT,
> ...etc...
>
> but Al felt that it was probably better to create an EIO-returner for each
> actual op signature. Since so few ops share a signature, I just went ahead
> & created an EIO function for each individual file & inode op that returns
> a value.
>
Al is correct, of course. But the patch takes bad_inode.o from 280 up to 703
bytes, which is a bit sad for some cosmetic thing which nobody ever looks
at or modifies.
Perhaps you can do
static int return_EIO_int(void)
{
return -EIO;
}
static int bad_file_release(struct inode * inode, struct file * filp)
__attribute__((alias("return_EIO_int")));
static int bad_file_fsync(struct inode * inode, struct file * filp)
__attribute__((alias("return_EIO_int")));
etcetera?
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