[PATCH -v2] x86, microcode, AMD: Sanity-check initrd image

[Borislav Petkov]

On Thu, Jan 30, 2014 at 08:54:13PM +0100, Borislav Petkov wrote:
> Yeah, it is simpler. Ok, will change.

Ok, let's have another run at it. This one takes care of the relocated
ramdisk on 64-bit too, as we do it there also, not only on 32-bit. It
boots fine here on the 32/64-bit guests.

---
From: Borislav Petkov <bp@xxxxxxx>
Subject: [PATCH] x86, microcode, AMD: Sanity-check initrd image

For additional coverage, BorisO and friends did swap AMD microcode with
Intel microcode blobs in order to see what happens. What did happen on
32-bit was

[    5.722656] BUG: unable to handle kernel paging request at be3a6008
[    5.722693] IP: [<c106d6b4>] load_microcode_amd+0x24/0x3f0
[    5.722716] *pdpt = 0000000000000000 *pde = 0000000000000000

because there was a valid initrd there but without valid microcode in
it. In order to fix that, we need to check the container signature from
the initrd before we continue loading it.

Also, take care of the ramdisk relocation on both bitness.

Reported-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 arch/x86/kernel/cpu/microcode/amd_early.c | 60 +++++++++++++++++++++++--------
 1 file changed, 45 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/amd_early.c b/arch/x86/kernel/cpu/microcode/amd_early.c
index 8384c0fa206f..41537ae7c31d 100644
--- a/arch/x86/kernel/cpu/microcode/amd_early.c
+++ b/arch/x86/kernel/cpu/microcode/amd_early.c
@@ -37,10 +37,12 @@ static __initdata char ucode_path[] = "kernel/x86/microcode/AuthenticAMD.bin";
 
 static struct cpio_data __init find_ucode_in_initrd(void)
 {
+	struct cpio_data ret;
 	long offset = 0;
 	char *path;
 	void *start;
 	size_t size;
+	u32 *hdr;
 
 #ifdef CONFIG_X86_32
 	struct boot_params *p;
@@ -59,7 +61,20 @@ static struct cpio_data __init find_ucode_in_initrd(void)
 	size    = boot_params.hdr.ramdisk_size;
 #endif
 
-	return find_cpio_data(path, start, size, &offset);
+	ret = find_cpio_data(path, start, size, &offset);
+	if (!ret.data)
+		return ret;
+
+	/* Verify we didn't get some garbage from the initrd. */
+	hdr = (u32 *)ret.data;
+
+	if (hdr[0] != UCODE_MAGIC ||
+	    hdr[1] != UCODE_EQUIV_CPU_TABLE_TYPE ||
+	    hdr[2] == 0) {
+		ret.data = NULL;
+		ret.size = 0;
+	}
+	return ret;
 }
 
 static size_t compute_container_size(u8 *data, u32 total_size)
@@ -285,6 +300,15 @@ static void __init collect_cpu_sig_on_bsp(void *arg)
 
 	uci->cpu_sig.sig = cpuid_eax(0x00000001);
 }
+
+static void __init get_bsp_sig(void)
+{
+	unsigned int bsp = boot_cpu_data.cpu_index;
+	struct ucode_cpu_info *uci = ucode_cpu_info + bsp;
+
+	if (!uci->cpu_sig.sig)
+		smp_call_function_single(bsp, collect_cpu_sig_on_bsp, NULL, 1);
+}
 #else
 void load_ucode_amd_ap(void)
 {
@@ -337,31 +361,37 @@ void load_ucode_amd_ap(void)
 
 int __init save_microcode_in_initrd_amd(void)
 {
+	unsigned long cont;
 	enum ucode_state ret;
 	u32 eax;
 
-#ifdef CONFIG_X86_32
-	unsigned int bsp = boot_cpu_data.cpu_index;
-	struct ucode_cpu_info *uci = ucode_cpu_info + bsp;
-
-	if (!uci->cpu_sig.sig)
-		smp_call_function_single(bsp, collect_cpu_sig_on_bsp, NULL, 1);
+	if (!container)
+		return -EINVAL;
 
+#ifdef CONFIG_X86_32
+	get_bsp_sig();
+	cont = (unsigned long)container;
+#else
 	/*
-	 * Take into account the fact that the ramdisk might get relocated
-	 * and therefore we need to recompute the container's position in
-	 * virtual memory space.
+	 * We need the physical address of the container for both bitness since
+	 * boot_params.hdr.ramdisk_image is a physical address.
 	 */
-	container = (u8 *)(__va((u32)relocated_ramdisk) +
-			   ((u32)container - boot_params.hdr.ramdisk_image));
+	cont = __pa(container);
 #endif
+
+	/*
+	 * Take into account the fact that the ramdisk might get relocated and
+	 * therefore we need to recompute the container's position in virtual
+	 * memory space.
+	 */
+	if (relocated_ramdisk)
+		container = (u8 *)(__va(relocated_ramdisk) +
+			     (cont - boot_params.hdr.ramdisk_image));
+
 	if (ucode_new_rev)
 		pr_info("microcode: updated early to new patch_level=0x%08x\n",
 			ucode_new_rev);
 
-	if (!container)
-		return -EINVAL;
-
 	eax   = cpuid_eax(0x00000001);
 	eax   = ((eax >> 8) & 0xf) + ((eax >> 20) & 0xff);
 
-- 
1.8.5.2.192.g7794a68

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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