linux-kernel - [PATCH 1/2] x86/microcode: Look for the initrd at the correct address on 32-bit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20170614140626.4462-1-bp@alien8.de>
Date:   Wed, 14 Jun 2017 16:06:25 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 1/2] x86/microcode: Look for the initrd at the correct address on 32-bit

From: Borislav Petkov <bp@...e.de>

Early during boot, the BSP finds the ramdisk's position from boot_params
but by the time the APs get to boot, the BSP has continued in the mean
time and has potentially managed to relocate that ramdisk.

And in that case, the APs need to find the ramdisk at its new position,
in *physical* memory as they're running before paging has been enabled.

Thus, get the updated physical location of the ramdisk which is in the
relocated_ramdisk variable.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/cpu/microcode/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index e53d3c909840..9cb98ee103db 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -290,6 +290,17 @@ struct cpio_data find_microcode_in_initrd(const char *path, bool use_pa)
 			return (struct cpio_data){ NULL, 0, "" };
 		if (initrd_start)
 			start = initrd_start;
+	} else {
+		/*
+		 * The picture with physical addresses is a bit different: we
+		 * need to get the *physical* address to which the ramdisk was
+		 * relocated, i.e., relocated_ramdisk (not initrd_start) and
+		 * since we're running from physical addresses, we need to access
+		 * relocated_ramdisk through its *physical* address too.
+		 */
+		u64 *rr = (u64 *)__pa_nodebug(&relocated_ramdisk);
+		if (*rr)
+			start = *rr;
 	}
 
 	return find_cpio_data(path, (void *)start, size, NULL);
-- 
2.13.0