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    SubjectRe: [PATCH] kernel 2.6.24.1 still vulnerable to the vmsplice local root exploit
    On Sun, Feb 10, 2008 at 04:40:53AM -0500, Niki Denev wrote:
    > this fixed the problem for me (kernel 2.6.24.1) :
    > It appears that the initial patch checked the input to vmsplice_to_user,
    > but the exploit used vmsplice_to_pipe which remained open to the attack.

    This patch is broken. It opens the old hole again.

    > @@ -1450,6 +1454,31 @@
    > .ops = &user_page_pipe_buf_ops,
    > };
    >
    > + error = ret = 0;
    > +
    > + /*
    > + * Get user address base and length for this iovec.
    > + */
    > + error = get_user(base, &iov->iov_base);
    > + if (unlikely(error))
    > + return error;
    > + error = get_user(len, &iov->iov_len);
    > + if (unlikely(error))
    > + return error;

    iov is unchecked.

    > + if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
    > + return -EFAULT;
    > + }

    Use VERIFY_READ and this only checks the first entry.

    I checked the following patch and it at least fixes the known exploit.

    diff --git a/fs/splice.c b/fs/splice.c
    index 14e2262..80beb2b 100644
    --- a/fs/splice.c
    +++ b/fs/splice.c
    @@ -1237,6 +1237,11 @@ static int get_iovec_page_array(const struct iovec __user *iov,
    if (unlikely(!base))
    break;

    + if (!access_ok(VERIFY_READ, base, len)) {
    + error = -EFAULT;
    + break;
    + }
    +
    /*
    * Get this base offset and number of pages, then map
    * in the user pages.
    --
    Even historians fail to learn from history -- they repeat the same mistakes.
    -- John Gill, "Patterns of Force", stardate 2534.7

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