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    SubjectRe: [PATCH 02/36] usercopy: Include offset in overflow report
    On Wed, Jan 10, 2018 at 7:25 AM, Christopher Lameter <cl@linux.com> wrote:
    > On Tue, 9 Jan 2018, Kees Cook wrote:
    >
    >> -static void report_usercopy(unsigned long len, bool to_user, const char *type)
    >> +int report_usercopy(const char *name, const char *detail, bool to_user,
    >> + unsigned long offset, unsigned long len)
    >> {
    >> - pr_emerg("kernel memory %s attempt detected %s '%s' (%lu bytes)\n",
    >> + pr_emerg("kernel memory %s attempt detected %s %s%s%s%s (offset %lu, size %lu)\n",
    >> to_user ? "exposure" : "overwrite",
    >> - to_user ? "from" : "to", type ? : "unknown", len);
    >> + to_user ? "from" : "to",
    >> + name ? : "unknown?!",
    >> + detail ? " '" : "", detail ? : "", detail ? "'" : "",
    >> + offset, len);
    >> /*
    >> * For greater effect, it would be nice to do do_group_exit(),
    >> * but BUG() actually hooks all the lock-breaking and per-arch
    >> * Oops code, so that is used here instead.
    >> */
    >> BUG();
    >
    > Should this be a WARN() or so? Or some configuration that changes
    > BUG() behavior? Otherwise

    This BUG() is the existing behavior, with the new behavior taking the
    WARN() route in a following patch.

    >> +
    >> + return -1;
    >
    > This return code will never be returned.
    >
    > Why a return code at all? Maybe I will see that in the following patches?

    I was trying to simplify the callers, but I agree, the result is
    rather ugly. I'll see if I can fix this up.

    -Kees

    --
    Kees Cook
    Pixel Security

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