From: Masami Hiramatsu <mhiramat@xxxxxxxxxx> commit 50b8a742850fce7293bed45753152c425f7e931b upstream. Since Grub may align the size of initrd to 4 if user pass initrd from cpio, we have to check the preceding 3 bytes as well. Link: https://lkml.kernel.org/r/160520205132.303174.4876760192433315429.stgit@devnote2 Cc: stable@xxxxxxxxxxxxxxx Fixes: 85c46b78da58 ("bootconfig: Add bootconfig magic word for indicating bootconfig explicitly") Reported-by: Chen Yu <yu.chen.surf@xxxxxxxxx> Tested-by: Chen Yu <yu.chen.surf@xxxxxxxxx> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- init/main.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) --- a/init/main.c +++ b/init/main.c @@ -267,14 +267,24 @@ static void * __init get_boot_config_fro u32 size, csum; char *data; u32 *hdr; + int i; if (!initrd_end) return NULL; data = (char *)initrd_end - BOOTCONFIG_MAGIC_LEN; - if (memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN)) - return NULL; + /* + * Since Grub may align the size of initrd to 4, we must + * check the preceding 3 bytes as well. + */ + for (i = 0; i < 4; i++) { + if (!memcmp(data, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN)) + goto found; + data--; + } + return NULL; +found: hdr = (u32 *)(data - 8); size = hdr[0]; csum = hdr[1];
