init/main: read bootconfig header with get_unaligned_le32()

get_boot_config_from_initrd() scans up to 3 bytes before initrd_end to
handle GRUB 4-byte alignment.  As a result, the bootconfig header
immediately preceding the magic may be unaligned.

Read the size and checksum fields with get_unaligned_le32() instead of
casting to u32 * and using le32_to_cpu(), avoiding potential unaligned
access and silencing sparse "cast to restricted __le32" warnings.

Sparse warnings (gcc + C=1):
  init/main.c:292:16: warning: cast to restricted __le32
  init/main.c:293:16: warning: cast to restricted __le32

No functional change intended.

Link: https://lkml.kernel.org/r/20260113101532.1630770-1-sun.jian.kdev@gmail.com
Signed-off-by: Sun Jian <sun.jian.kdev@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/init/main.c b/init/main.c
index 4773f3bad49c429d8bf7dc3f412894b277eb7497..29741049aa7977edd10f53240352248d2d1ad12b 100644 (file)
--- a/init/main.c
+++ b/init/main.c
@@ -104,6 +104,7 @@
 #include <linux/pidfs.h>
 #include <linux/ptdump.h>
 #include <linux/time_namespace.h>
+#include <linux/unaligned.h>
 #include <net/net_namespace.h>
 
 #include <asm/io.h>
@@ -270,7 +271,7 @@ static void * __init get_boot_config_from_initrd(size_t *_size)
 {
        u32 size, csum;
        char *data;
-       u32 *hdr;
+       u8 *hdr;
        int i;
 
        if (!initrd_end)
@@ -289,9 +290,9 @@ static void * __init get_boot_config_from_initrd(size_t *_size)
        return NULL;
 
 found:
-       hdr = (u32 *)(data - 8);
-       size = le32_to_cpu(hdr[0]);
-       csum = le32_to_cpu(hdr[1]);
+       hdr = (u8 *)(data - 8);
+       size = get_unaligned_le32(hdr);
+       csum = get_unaligned_le32(hdr + 4);
 
        data = ((void *)hdr) - size;
        if ((unsigned long)data < initrd_start) {