[PATCH v4 3/4] fanotify,audit: Allow audit to use the full permission event response

[Richard Guy Briggs]

This patch passes the full value so that the audit function can use all
of it. The audit function was updated to log the additional information in
the AUDIT_FANOTIFY record. The following is an example of the new record
format:

type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=17

Suggested-by: Steve Grubb <sgrubb@xxxxxxxxxx>
Link: https://lore.kernel.org/r/3075502.aeNJFYEL58@x2
Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
---
 fs/notify/fanotify/fanotify.c |  3 ++-
 include/linux/audit.h         |  9 +++++----
 kernel/auditsc.c              | 31 ++++++++++++++++++++++++++++---
 3 files changed, 35 insertions(+), 8 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 0f36062521f4..36c3ed1af085 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -276,7 +276,8 @@ static int fanotify_get_response(struct fsnotify_group *group,
 
 	/* Check if the response should be audited */
 	if (event->response & FAN_AUDIT)
-		audit_fanotify(event->response & ~FAN_AUDIT);
+		audit_fanotify(event->response & ~FAN_AUDIT,
+			       event->info_len, event->info_buf);
 
 	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
 		 group, event, ret);
diff --git a/include/linux/audit.h b/include/linux/audit.h
index 3ea198a2cd59..c69efdba12ca 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -14,6 +14,7 @@
 #include <linux/audit_arch.h>
 #include <uapi/linux/audit.h>
 #include <uapi/linux/netfilter/nf_tables.h>
+#include <uapi/linux/fanotify.h>
 
 #define AUDIT_INO_UNSET ((unsigned long)-1)
 #define AUDIT_DEV_UNSET ((dev_t)-1)
@@ -417,7 +418,7 @@ extern void __audit_log_capset(const struct cred *new, const struct cred *old);
 extern void __audit_mmap_fd(int fd, int flags);
 extern void __audit_openat2_how(struct open_how *how);
 extern void __audit_log_kern_module(char *name);
-extern void __audit_fanotify(u32 response);
+extern void __audit_fanotify(u32 response, size_t len, char *buf);
 extern void __audit_tk_injoffset(struct timespec64 offset);
 extern void __audit_ntp_log(const struct audit_ntp_data *ad);
 extern void __audit_log_nfcfg(const char *name, u8 af, unsigned int nentries,
@@ -524,10 +525,10 @@ static inline void audit_log_kern_module(char *name)
 		__audit_log_kern_module(name);
 }
 
-static inline void audit_fanotify(u32 response)
+static inline void audit_fanotify(u32 response, size_t len, char *buf)
 {
 	if (!audit_dummy_context())
-		__audit_fanotify(response);
+		__audit_fanotify(response, len, buf);
 }
 
 static inline void audit_tk_injoffset(struct timespec64 offset)
@@ -684,7 +685,7 @@ static inline void audit_log_kern_module(char *name)
 {
 }
 
-static inline void audit_fanotify(u32 response)
+static inline void audit_fanotify(u32 response, size_t len, char *buf)
 { }
 
 static inline void audit_tk_injoffset(struct timespec64 offset)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index 433418d73584..f000fec52360 100644
--- a/kernel/auditsc.c
+++ b/kernel/auditsc.c
@@ -64,6 +64,7 @@
 #include <uapi/linux/limits.h>
 #include <uapi/linux/netfilter/nf_tables.h>
 #include <uapi/linux/openat2.h> // struct open_how
+#include <uapi/linux/fanotify.h>
 
 #include "audit.h"
 
@@ -2899,10 +2900,34 @@ void __audit_log_kern_module(char *name)
 	context->type = AUDIT_KERN_MODULE;
 }
 
-void __audit_fanotify(u32 response)
+void __audit_fanotify(u32 response, size_t len, char *buf)
 {
-	audit_log(audit_context(), GFP_KERNEL,
-		AUDIT_FANOTIFY,	"resp=%u", response);
+	struct fanotify_response_info_audit_rule *friar;
+	size_t c = len;
+	char *ib = buf;
+
+	if (!(len && buf)) {
+		audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
+			  "resp=%u fan_type=0 fan_info=?", response);
+		return;
+	}
+	while (c >= sizeof(struct fanotify_response_info_header)) {
+		friar = (struct fanotify_response_info_audit_rule *)buf;
+		switch (friar->hdr.type) {
+		case FAN_RESPONSE_INFO_AUDIT_RULE:
+			if (friar->hdr.len < sizeof(*friar)) {
+				audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
+					  "resp=%u fan_type=%u fan_info=(incomplete)",
+					  response, friar->hdr.type);
+				return;
+			}
+			audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
+				  "resp=%u fan_type=%u fan_info=%u",
+				  response, friar->hdr.type, friar->audit_rule);
+		}
+		c -= friar->hdr.len;
+		ib += friar->hdr.len;
+	}
 }
 
 void __audit_tk_injoffset(struct timespec64 offset)
-- 
2.27.0