Re: [PATCH] RDMA/ucma: check fd type in ucma_migrate_id()

[Jason Gunthorpe]

On Mon, Sep 03, 2018 at 06:54:14PM +0200, Jann Horn wrote:
> The current code grabs the private_data of whatever file descriptor
> userspace has supplied and implicitly casts it to a `struct ucma_file *`,
> potentially causing a type confusion.
> 
> This is probably fine in practice because the pointer is only used for
> comparisons, it is never actually dereferenced; and even in the
> comparisons, it is unlikely that a file from another filesystem would have
> a ->private_data pointer that happens to also be valid in this context.
> But ->private_data is not always guaranteed to be a valid pointer to an
> object owned by the file's filesystem; for example, some filesystems just
> cram numbers in there.
> 
> Check the type of the supplied file descriptor to be safe, analogous to how
> other places in the kernel do it.
> 
> Fixes: 88314e4dda1e ("RDMA/cma: add support for rdma_migrate_id()")
> Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
> ---
> Only compile-tested, because I don't have an environment in which I
> could test this.
> 
>  drivers/infiniband/core/ucma.c | 6 ++++++
>  1 file changed, 6 insertions(+)

Yep, this looks right to me also, applied to for-rc, thanks

Jason