Messages in this thread Patch in this message | | | Date | Thu, 4 Apr 2019 18:27:53 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/microcode: Refactor Intel microcode loading |
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On Thu, Apr 04, 2019 at 01:11:28PM +0200, Jann Horn wrote: > This changes generic_load_microcode() to use the iov_iter API instead of > an open-coded version. This allows us to avoid explicitly casting between > user and kernel pointers. > > Because the iov_iter API makes it hard to read the same location twice, as > a side effect, this also fixes a double-read of the microcode header (which > could e.g. lead to out-of-bounds reads in microcode_sanity_check()). > Not that it matters much, only root can do this anyway... > > Signed-off-by: Jann Horn <jannh@google.com> > --- > I have tested that with this patch applied, microcode loading still works > both via "iucode-tool -k" and via > /sys/devices/system/cpu/microcode/reload.
Yeah, this cannot have worked because I think I broke it recently and you'd need this:
--- diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 5260185cbf7b..8a4a7823451a 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -418,8 +418,9 @@ static int do_microcode_update(const void __user *buf, size_t size) if (ustate == UCODE_ERROR) { error = -1; break; - } else if (ustate == UCODE_OK) + } else if (ustate == UCODE_NEW) { apply_microcode_on_target(cpu); + } } return error; --- Regardless, I'll take care of it. Thanks a lot for doing this cleanup, it looks really cool and nicely clean - exactly how I envisioned it. :-)
I'll test it more later with the above fix and apply it.
Thx.
-- Regards/Gruss, Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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