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    SubjectRe: [PATCH 03/24] net: add a new sockptr_t type
    On Mon, Jul 20, 2020 at 07:43:22PM +0200, Christoph Hellwig wrote:
    > On Mon, Jul 20, 2020 at 09:37:48AM -0700, Eric Biggers wrote:
    > > How does this not introduce a massive security hole when
    > > CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE?
    > >
    > > AFAICS, userspace can pass in a pointer >= TASK_SIZE,
    > > and this code makes it be treated as a kernel pointer.
    >
    > Yeah, we'll need to validate that before initializing the pointer.
    >
    > But thinking this a little further: doesn't this mean any
    > set_fs(KERNEL_DS) that has other user pointers than the one it is
    > intended for has the same issue? Pretty much all of these are gone
    > in mainline now, but in older stable kernels there might be some
    > interesting cases, especially in the compat ioctl handlers.

    Yes. I thought that eliminating that class of bug is one of the main
    motivations for your "remove set_fs" work. See commit 128394eff343
    ("sg_write()/bsg_write() is not fit to be called under KERNEL_DS") for a case
    where this type of bug was fixed.

    Are you aware of any specific cases that weren't already fixed? If there are
    any, they need to be urgently fixed.

    - Eric

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