initramfs: avoid memcpy for hex header fields

newc/crc cpio headers contain a bunch of 8-character hexadecimal fields
which we convert via simple_strtoul(), following memcpy() into a
zero-terminated stack buffer. The new simple_strntoul() helper allows us
to pass in max_chars=8 to avoid zero-termination and memcpy().

Signed-off-by: David Disseldorp <ddiss@suse.de>
Link: https://lore.kernel.org/r/20250304061020.9815-5-ddiss@suse.de
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/init/initramfs.c b/init/initramfs.c
index 002e83ae12ac7586cc1bd9328f24505d5d6823da..6dd3b02c15d7ecb4ededf0ac29c7616ccd4a9d21 100644 (file)
--- a/init/initramfs.c
+++ b/init/initramfs.c
@@ -189,14 +189,11 @@ static __initdata u32 hdr_csum;
 static void __init parse_header(char *s)
 {
        unsigned long parsed[13];
-       char buf[9];
        int i;
 
-       buf[8] = '\0';
-       for (i = 0, s += 6; i < 13; i++, s += 8) {
-               memcpy(buf, s, 8);
-               parsed[i] = simple_strtoul(buf, NULL, 16);
-       }
+       for (i = 0, s += 6; i < 13; i++, s += 8)
+               parsed[i] = simple_strntoul(s, NULL, 16, 8);
+
        ino = parsed[0];
        mode = parsed[1];
        uid = parsed[2];