kbuild: modversions: Fix relative CRC byte order interpretation

BugLink: https://bugs.launchpad.net/bugs/1823060
commit 54a7151b1496cddbb7a83546b7998103e98edc88 upstream.

Fix commit 56067812d5b0 ("kbuild: modversions: add infrastructure for
emitting relative CRCs") where CRCs are interpreted in host byte order
rather than proper kernel byte order. The bug is conditional on
CONFIG_MODULE_REL_CRCS.

For example, when loading a BE module into a BE kernel compiled with a LE
system, the error "disagrees about version of symbol module_layout" is
produced. A message such as "Found checksum D7FA6856 vs module 5668FAD7"
will be given with debug enabled, which indicates an obvious endian
problem within __kcrctab within the kernel image.

The general solution is to use the macro TO_NATIVE, as is done in
similar cases throughout modpost.c. With this correction it has been
verified that a BE kernel compiled with a LE system accepts BE modules.

This change has also been verified with a LE kernel compiled with a LE
system, in which case TO_NATIVE returns its value unmodified since the
byte orders match. This is by far the common case.

Fixes: 56067812d5b0 ("kbuild: modversions: add infrastructure for emitting relative CRCs")
Signed-off-by: Fredrik Noring <noring@nocrew.org>
Cc: stable@vger.kernel.org
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 26bf886bd168828ccf750554aa7e28ffac6f6a8c..588a3bc29ecc4fe6b7f5138e5f0cdc66a5c61ae8 100644 (file)
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -640,7 +640,7 @@ static void handle_modversions(struct module *mod, struct elf_info *info,
                               info->sechdrs[sym->st_shndx].sh_offset -
                               (info->hdr->e_type != ET_REL ?
                                info->sechdrs[sym->st_shndx].sh_addr : 0);
-                       crc = *crcp;
+                       crc = TO_NATIVE(*crcp);
                }
                sym_update_crc(symname + strlen("__crc_"), mod, crc,
                                export);