From: David Disseldorp Subject: initramfs: refactor do_header() cpio magic checks Patch series "initramfs: "crc" cpio format and INITRAMFS_PRESERVE_MTIME", v7. This patchset does some minor initramfs refactoring and allows cpio entry mtime preservation to be disabled via a new Kconfig INITRAMFS_PRESERVE_MTIME option. Patches 4/6 to 6/6 implement support for creation and extraction of "crc" cpio archives, which carry file data checksums. Basic tests for this functionality can be found at https://github.com/rapido-linux/rapido/pull/163 This patch (of 6): do_header() is called for each cpio entry and fails if the first six bytes don't match "newc" magic. The magic check includes a special case error message if POSIX.1 ASCII (cpio -H odc) magic is detected. This special case POSIX.1 check can be nested under the "newc" mismatch code path to avoid calling memcmp() twice in a non-error case. Link: https://lkml.kernel.org/r/20220404093429.27570-1-ddiss@suse.de Link: https://lkml.kernel.org/r/20220404093429.27570-2-ddiss@suse.de Signed-off-by: David Disseldorp Reviewed-by: Martin Wilck Acked-by: Christian Brauner Cc: Al Viro Cc: Matthew Wilcox Signed-off-by: Andrew Morton --- init/initramfs.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) --- a/init/initramfs.c~initramfs-refactor-do_header-cpio-magic-checks +++ a/init/initramfs.c @@ -257,12 +257,11 @@ static int __init do_collect(void) static int __init do_header(void) { - if (memcmp(collected, "070707", 6)==0) { - error("incorrect cpio method used: use -H newc option"); - return 1; - } if (memcmp(collected, "070701", 6)) { - error("no cpio magic"); + if (memcmp(collected, "070707", 6) == 0) + error("incorrect cpio method used: use -H newc option"); + else + error("no cpio magic"); return 1; } parse_header(collected); _