[PATCH v2 10/19] module: skip modversion checks for crypto modules

[Jay Wang]

The standalone crypto module feature allows loading pre-built crypto
modules from an external build to preserve FIPS certification across
kernel updates. Since these externally built modules have different
modversion CRCs than the running kernel, the module_layout and per-symbol
version checks will fail.

Add a flags field to struct load_info and bypass check_version() and
check_modstruct_version() for crypto modules. For fips140.ko loaded
from embedded kernel memory, the MODULE_INIT_CRYPTO_FROM_MEM flag is set
by the loader. For individual crypto algorithm modules (e.g., authenc.ko,
ccm.ko) built with the crypto-objs-m rule, a .fips140_crypto_marker ELF
section is detected during early_mod_check() and the
MODULE_INIT_CRYPTO_OBJS_M flag is set accordingly.

Signed-off-by: Jay Wang <wanjay at amazon.com>
---
 include/uapi/linux/module.h |  1 +
 kernel/module/internal.h    |  1 +
 kernel/module/main.c        | 17 +++++++++++++++++
 kernel/module/version.c     |  9 +++++++++
 4 files changed, 28 insertions(+)

diff --git a/include/uapi/linux/module.h b/include/uapi/linux/module.h
index 6941497350893..7c6b3ae55c8d7 100644
--- a/include/uapi/linux/module.h
+++ b/include/uapi/linux/module.h
@@ -10,6 +10,7 @@
 #ifdef __KERNEL__
 /* Internal flags */
 #define MODULE_INIT_CRYPTO_FROM_MEM		(1 << 8)
+#define MODULE_INIT_CRYPTO_OBJS_M		(1 << 9)
 #endif
 
 #endif /* _UAPI_LINUX_MODULE_H */
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index 061161cc79d90..b75b19e0b5dcf 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -69,6 +69,7 @@ struct load_info {
 	char *secstrings, *strtab;
 	unsigned long symoffs, stroffs, init_typeoffs, core_typeoffs;
 	bool sig_ok;
+	int flags;
 #ifdef CONFIG_KALLSYMS
 	unsigned long mod_kallsyms_init_off;
 #endif
diff --git a/kernel/module/main.c b/kernel/module/main.c
index 6152b9b39e6b1..69949069dc5f5 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -3446,6 +3446,22 @@ static int early_mod_check(struct load_info *info, int flags)
 	if (err)
 		return err;
 
+#ifdef CONFIG_CRYPTO_FIPS140_EXTMOD
+	/* Detect crypto-objs-m modules by .fips140_crypto_marker section */
+	if (!(info->flags & MODULE_INIT_CRYPTO_FROM_MEM)) {
+		unsigned int i;
+
+		for (i = 1; i < info->hdr->e_shnum; i++) {
+			const char *sname = info->secstrings + info->sechdrs[i].sh_name;
+
+			if (strcmp(sname, ".fips140_crypto_marker") == 0) {
+				info->flags |= MODULE_INIT_CRYPTO_OBJS_M;
+				break;
+			}
+		}
+	}
+#endif
+
 	/* Check module struct version now, before we try to use module. */
 	if (!check_modstruct_version(info, info->mod))
 		return -ENOEXEC;
@@ -3678,6 +3694,7 @@ int load_crypto_module_mem(const char *mem, size_t size)
 	}
 
 	info.sig_ok = true;
+	info.flags = MODULE_INIT_CRYPTO_FROM_MEM;
 	info.hdr = (Elf_Ehdr *) mem;
 	info.len = size;
 
diff --git a/kernel/module/version.c b/kernel/module/version.c
index 2beefeba82d94..3c5b5fceb73a9 100644
--- a/kernel/module/version.c
+++ b/kernel/module/version.c
@@ -8,6 +8,7 @@
 #include <linux/module.h>
 #include <linux/string.h>
 #include <linux/printk.h>
+#include <uapi/linux/module.h>
 #include "internal.h"
 
 int check_version(const struct load_info *info,
@@ -21,6 +22,10 @@ int check_version(const struct load_info *info,
 	struct modversion_info *versions;
 	struct modversion_info_ext version_ext;
 
+	/* Skip version checks for FIPS crypto modules */
+	if (info->flags & (MODULE_INIT_CRYPTO_FROM_MEM | MODULE_INIT_CRYPTO_OBJS_M))
+		return 1;
+
 	/* Exporting module didn't supply crcs?  OK, we're already tainted. */
 	if (!crc)
 		return 1;
@@ -81,6 +86,10 @@ int check_modstruct_version(const struct load_info *info,
 	};
 	bool have_symbol;
 
+	/* Skip module_layout version check for FIPS crypto modules */
+	if (info->flags & (MODULE_INIT_CRYPTO_FROM_MEM | MODULE_INIT_CRYPTO_OBJS_M))
+		return 1;
+
 	/*
 	 * Since this should be found in kernel (which can't be removed), no
 	 * locking is necessary. Regardless use a RCU read section to keep
-- 
2.47.3