bootconfig: Fix to remove bootconfig data from initrd while boot

If there is a bootconfig data in the tail of initrd/initramfs,
initrd image sanity check caused an error while decompression
stage as follows.

[    0.883882] Unpacking initramfs...
[    2.696429] Initramfs unpacking failed: invalid magic at start of compressed archive

This error will be ignored if CONFIG_BLK_DEV_RAM=n,
but CONFIG_BLK_DEV_RAM=y the kernel failed to mount rootfs
and causes a panic.

To fix this issue, shrink down the initrd_end for removing
tailing bootconfig data while boot the kernel.

Link: http://lkml.kernel.org/r/158788401014.24243.17424755854115077915.stgit@devnote2

Cc: Borislav Petkov <bp@alien8.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: stable@vger.kernel.org
Fixes: 7684b858 ("bootconfig: Load boot config from the tail of initrd")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

init/main.c

@@ -257,6 +257,47 @@ static int __init loglevel(char *str)
 
 early_param("loglevel", loglevel);
 
+#ifdef CONFIG_BLK_DEV_INITRD
+static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
+{
+	u32 size, csum;
+	char *data;
+	u32 *hdr;
+
+	if (!initrd_end)
+		return NULL;
+
+	data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN;
+	if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN))
+		return NULL;
+
+	hdr = (u32 *)(data - 8);
+	size = hdr[0];
+	csum = hdr[1];
+
+	data = ((void *)hdr) - size;
+	if ((unsigned long)data < initrd_start) {
+		pr_err("bootconfig size %d is greater than initrd size %ld\n",
+			size, initrd_end - initrd_start);
+		return NULL;
+	}
+
+	/* Remove bootconfig from initramfs/initrd */
+	initrd_end = (unsigned long)data;
+	if (_size)
+		*_size = size;
+	if (_csum)
+		*_csum = csum;
+
+	return data;
+}
+#else
+static void * __init get_boot_config_from_initrd(u32 *_size, u32 *_csum)
+{
+	return NULL;
+}
+#endif
+
 #ifdef CONFIG_BOOT_CONFIG
 
 char xbc_namebuf[XBC_KEYLEN_MAX] __initdata;
@@ -357,9 +398,12 @@ static void __init setup_boot_config(const char *cmdline)
 	int pos;
 	u32 size, csum;
 	char *data, *copy;
-	u32 *hdr;
 	int ret;
 
+	data = get_boot_config_from_initrd(&size, &csum);
+	if (!data)
+		goto not_found;
+
 	strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);
 	parse_args("bootconfig", tmp_cmdline, NULL, 0, 0, 0, NULL,
 		   bootconfig_params);
@@ -367,27 +411,12 @@ static void __init setup_boot_config(const char *cmdline)
 	if (!bootconfig_found)
 		return;
 
-	if (!initrd_end)
-		goto not_found;
-
-	data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN;
-	if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN))
-		goto not_found;
-
-	hdr = (u32 *)(data - 8);
-	size = hdr[0];
-	csum = hdr[1];
-
 	if (size >= XBC_DATA_MAX) {
 		pr_err("bootconfig size %d greater than max size %d\n",
 			size, XBC_DATA_MAX);
 		return;
 	}
 
-	data = ((void *)hdr) - size;
-	if ((unsigned long)data < initrd_start)
-		goto not_found;
-
 	if (boot_config_checksum((unsigned char *)data, size) != csum) {
 		pr_err("bootconfig checksum failed\n");
 		return;
@@ -420,8 +449,14 @@ static void __init setup_boot_config(const char *cmdline)
 not_found:
 	pr_err("'bootconfig' found on command line, but no bootconfig found\n");
 }
+
 #else
-#define setup_boot_config(cmdline)	do { } while (0)
+
+static void __init setup_boot_config(const char *cmdline)
+{
+	/* Remove bootconfig data from initrd */
+	get_boot_config_from_initrd(NULL, NULL);
+}
 
 static int __init warn_bootconfig(char *str)
 {