libkmod: Fix unaligned access

From Jan Engelhardt:

	Program received signal SIGBUS, Bus error.
	[Switching to process 11100]
	0x00035278 in kmod_module_signature_info (file=0x4eeb8, sig_info=0xffffc254)
	    at libkmod/libkmod-signature.c:124
	124             sig_len = be32toh(modsig->sig_len);
	(gdb) p modsig
	$1 = (const struct module_signature *) 0xf7dfe143

modsig->sig_len can be unaligned if modsig is unaligned, so the padding
in the struct has no effect since we are mapping it to the mem buffer.

diff --git a/libkmod/libkmod-signature.c b/libkmod/libkmod-signature.c
index 6237ab7..a3ac15e 100644 (file)
--- a/libkmod/libkmod-signature.c
+++ b/libkmod/libkmod-signature.c
@@ -121,7 +121,7 @@ bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signat
                        modsig->hash >= PKEY_HASH__LAST ||
                        modsig->id_type >= PKEY_ID_TYPE__LAST)
                return false;
-       sig_len = be32toh(modsig->sig_len);
+       sig_len = be32toh(get_unaligned(&modsig->sig_len));
        if (size < (off_t)(modsig->signer_len + modsig->key_id_len + sig_len))
                return false;