On 01/30/2014 10:13 AM, Borislav Petkov wrote:
On Wed, Jan 29, 2014 at 12:22:19AM +0100, Borislav Petkov wrote:
Are you sure that
container = (u8 *)(__va((u32)relocated_ramdisk) +
((u32)container -
boot_params.hdr.ramdisk_image));
in save_microcode_in_initrd_amd() always results in a valid
pointer? It is non-NULL but it
points to address that looks to be not mapped.
Well, here's what I see here:
* initrd *without* microcode:
[ 0.000000] RAMDISK: [mem 0x7fbfc000-0x7ffeffff]
[ 0.000000] Allocated new RAMDISK: [mem 0x3680a000-0x36bfd099]
[ 0.000000] Move RAMDISK from [mem 0x7fbfc000-0x7ffef099] to [mem
0x3680a000-0x36bfd099]
...
[ 0.710771] save_microcode_in_initrd_amd:
relocated_ramdisk: 0x3680a000,
__va(relocated_ramdisk): 0xf680a000,
container: 0x76c0e000,
boot_params.hdr.ramdisk_image: 0x7fbfc000
...
[ 0.717080] BUG: unable to handle kernel paging request at 76c0e008
* initrd + microcode:
[ 0.000000] RAMDISK: [mem 0x7fbf7000-0x7ffeffff]
[ 0.000000] Allocated new RAMDISK: [mem 0x36805000-0x36bfd499]
[ 0.000000] Move RAMDISK from [mem 0x7fbf7000-0x7ffef499] to [mem
0x36805000-0x36bfd499]
[ 0.781948] save_microcode_in_initrd_amd:
relocated_ramdisk: 0x36805000,
__va(relocated_ramdisk): 0xf6805000,
container: 0xf680527c,
boot_params.hdr.ramdisk_image: 0x7fbf7000
Now guess what happens arithmetically if container is 0 (first case
above without microcode):
0xf680a000 + 0 - 0x7fbfc000 = 0x76c0e000.
So the fix of looking at ucode_cpio.data is correct.
That's not sufficient though, you'll need the other piece in
find_ucode_in_initrd() where you check the header.
An equivalent fix would be this hunk below but the initial version I
sent you aligns more with what we do on 64-bit.
---
diff --git a/arch/x86/kernel/cpu/microcode/amd_early.c
b/arch/x86/kernel/cpu/microcode/amd_early.c
index 8384c0fa206f..7199953fdbf2 100644
--- a/arch/x86/kernel/cpu/microcode/amd_early.c
+++ b/arch/x86/kernel/cpu/microcode/amd_early.c
@@ -347,6 +347,9 @@ int __init save_microcode_in_initrd_amd(void)
if (!uci->cpu_sig.sig)
smp_call_function_single(bsp, collect_cpu_sig_on_bsp, NULL, 1);
+ if (!container)
+ return -EINVAL;
+
/*
* Take into account the fact that the ramdisk might get relocated
* and therefore we need to recompute the container's position in
I like this one better. You can move this check above "#ifdef
CONFIG_X86_32" and have it as the first statement in the routine, common
between 32- and 64-bit.
-boris
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