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?
---
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 */
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
