[PATCH v7 3/3] fanotify, audit: Allow audit to use the full permission event response

[Richard Guy Briggs]

This patch passes the full response 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.

Currently the only type of fanotify info that is defined is an audit
rule number, but convert it to hex encoding to future-proof the field.
Hex encoding suggested by Paul Moore <p...@paul-moore.com>.

The {subj,obj}_trust values are {0,1,2}, corresponding to no, yes, unknown.

Sample records:
  type=FANOTIFY msg=audit(1600385147.372:590): resp=2 fan_type=1 fan_info=3137 
subj_trust=3 obj_trust=5
  type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 fan_info=0 
subj_trust=2 obj_trust=2

Suggested-by: Steve Grubb <sgr...@redhat.com>
Link: https://lore.kernel.org/r/3075502.aeNJFYEL58@x2
Signed-off-by: Richard Guy Briggs <r...@redhat.com>
---
 fs/notify/fanotify/fanotify.c |  3 ++-
 include/linux/audit.h         |  9 +++++----
 kernel/auditsc.c              | 18 +++++++++++++++---
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 24ec1d66d5a8..29bdd99b29fa 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -273,7 +273,8 @@ 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->audit_rule);
 
        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 d6b7d0c7ce43..31086a72e32a 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)
@@ -416,7 +417,7 @@ 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, struct 
fanotify_response_info_audit_rule *friar);
 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,
@@ -523,10 +524,10 @@ 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, struct 
fanotify_response_info_audit_rule *friar)
 {
        if (!audit_dummy_context())
-               __audit_fanotify(response);
+               __audit_fanotify(response, friar);
 }
 
 static inline void audit_tk_injoffset(struct timespec64 offset)
@@ -679,7 +680,7 @@ static inline void audit_log_kern_module(char *name)
 {
 }
 
-static inline void audit_fanotify(u32 response)
+static inline void audit_fanotify(u32 response, struct 
fanotify_response_info_audit_rule *friar)
 { }
 
 static inline void audit_tk_injoffset(struct timespec64 offset)
diff --git a/kernel/auditsc.c b/kernel/auditsc.c
index d1fb821de104..5a5994659b44 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"
 
@@ -2877,10 +2878,21 @@ void __audit_log_kern_module(char *name)
        context->type = AUDIT_KERN_MODULE;
 }
 
-void __audit_fanotify(u32 response)
+void __audit_fanotify(u32 response, struct fanotify_response_info_audit_rule 
*friar)
 {
-       audit_log(audit_context(), GFP_KERNEL,
-               AUDIT_FANOTIFY, "resp=%u", response);
+       /* {subj,obj}_trust values are {0,1,2}: no,yes,unknown */
+       switch (friar->hdr.type) {
+       case FAN_RESPONSE_INFO_NONE:
+               audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
+                         "resp=%u fan_type=%u fan_info=0 subj_trust=2 
obj_trust=2",
+                         response, FAN_RESPONSE_INFO_NONE);
+               break;
+       case FAN_RESPONSE_INFO_AUDIT_RULE:
+               audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY,
+                         "resp=%u fan_type=%u fan_info=%X subj_trust=%u 
obj_trust=%u",
+                         response, friar->hdr.type, friar->rule_number,
+                         friar->subj_trust, friar->obj_trust);
+       }
 }
 
 void __audit_tk_injoffset(struct timespec64 offset)
-- 
2.27.0

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