From: Andrey Ryabinin <aryabinin@virtuozzo.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: x86/microcode: use-after-free after cpu offline/online
Date: Wed, 25 Jan 2017 22:14:50 +0300 [thread overview]
Message-ID: <16165aad-5990-51f9-4dc7-c4b68597a4d5@virtuozzo.com> (raw)
In-Reply-To: <20170125172321.fpy6cswq3ibqvfgo@pd.tnic>
On 01/25/2017 08:23 PM, Borislav Petkov wrote:
> On Wed, Jan 25, 2017 at 07:58:39PM +0300, Andrey Ryabinin wrote:
>> On 4.10-rc5
>> # echo 0 > /sys/devices/system/cpu/cpu1/online
>> # echo 1 > /sys/devices/system/cpu/cpu1/online
>>
>> triggers use-after-free (probably caused by 06b8534cb72 "x86/microcode: Rework microcode loading").
>>
>> __load_ucode_intel() accesses initrd which is obviously gone at this point:
>
> Does that help?
Yup.
Tested-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>
> ---
> diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
> index 2af69d27da62..fdbf8d29ffcf 100644
> --- a/arch/x86/kernel/cpu/microcode/core.c
> +++ b/arch/x86/kernel/cpu/microcode/core.c
> @@ -248,8 +248,12 @@ struct cpio_data find_microcode_in_initrd(const char *path, bool use_pa)
> * possibly relocates the ramdisk. In either case, initrd_start contains
> * the updated address so use that instead.
> */
> - if (!use_pa && initrd_start)
> - start = initrd_start;
> + if (!use_pa) {
> + if (initrd_start)
> + start = initrd_start;
> + else
> + return (struct cpio_data){ NULL, 0, "" };
> + }
>
> return find_cpio_data(path, (void *)start, size, NULL);
> #else /* !CONFIG_BLK_DEV_INITRD */
>
next prev parent reply other threads:[~2017-01-25 19:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-25 16:58 x86/microcode: use-after-free after cpu offline/online Andrey Ryabinin
2017-01-25 17:23 ` Borislav Petkov
2017-01-25 19:14 ` Andrey Ryabinin [this message]
2017-01-25 19:23 ` Borislav Petkov
2017-01-26 16:58 ` [PATCH] x86/microcode: Do not access the initrd after it has been freed Borislav Petkov
2017-01-27 8:14 ` Andrey Ryabinin
2017-01-27 9:09 ` Borislav Petkov
2017-01-30 8:46 ` Ingo Molnar
2017-01-30 9:35 ` Borislav Petkov
2017-01-31 7:43 ` Ingo Molnar
2017-01-31 10:01 ` Borislav Petkov
2017-01-31 11:31 ` Mike Galbraith
2017-01-31 12:31 ` Borislav Petkov
2017-01-31 17:49 ` Borislav Petkov
2017-01-31 18:05 ` Mike Galbraith
2017-01-31 18:03 ` Thomas Gleixner
2017-01-31 19:25 ` [tip:irq/urgent] x86/irq: Make irq activate operations symmetric tip-bot for Thomas Gleixner
2017-01-31 16:39 ` [PATCH] x86/microcode: Do not access the initrd after it has been freed Ingo Molnar
2017-01-30 8:49 ` [tip:x86/microcode] " tip-bot for Borislav Petkov
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