[RFC v2 4/7] modsig: add integrity_module_check hook

[Dmitry Kasatkin]

IMA measures/appraises modules when modprobe or insmod opens and read them.
Unfortunately, there are no guarantees between what is read by userspace and
what is passed to the kernel via load_module system call. This patch adds a
hook called integrity_module_check() to verify the integrity of the module
being loaded.

Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx>
---
 include/linux/integrity.h |   10 ++++++++++
 kernel/module.c           |    9 +++++++++
 2 files changed, 19 insertions(+)

diff --git a/include/linux/integrity.h b/include/linux/integrity.h
index 66c5fe9..a80ec06 100644
--- a/include/linux/integrity.h
+++ b/include/linux/integrity.h
@@ -37,4 +37,14 @@ static inline void integrity_inode_free(struct inode *inode)
 	return;
 }
 #endif /* CONFIG_INTEGRITY_H */
+
+#ifdef CONFIG_INTEGRITY_MODULES
+int integrity_module_check(const void *hdr, const unsigned long len);
+#else
+static inline int integrity_module_check(const void *buf, unsigned long len)
+{
+	return 0;
+}
+#endif
+
 #endif /* _LINUX_INTEGRITY_H */
diff --git a/kernel/module.c b/kernel/module.c
index 4edbd9c..791da47 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -58,6 +58,7 @@
 #include <linux/jump_label.h>
 #include <linux/pfn.h>
 #include <linux/bsearch.h>
+#include <linux/integrity.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/module.h>
@@ -2437,6 +2438,14 @@ static int copy_and_check(struct load_info *info,
 
 	info->hdr = hdr;
 	info->len = len;
+
+	err = integrity_module_check(hdr, len);
+	if (err < 0)
+		goto free_hdr;
+
+	/* cut signature tail */
+	info->len = err;
+
 	return 0;
 
 free_hdr:
-- 
1.7.9.5

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