Re: [PATCH v4 4/4] fanotify, audit: deliver fan_info as a hex-encoded string

Hello Richard, Although I have it working, I have some comments below that might improve things. On Tuesday, August 9, 2022 1:22:55 PM EDT Richard Guy Briggs wrote: > 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. > > Sample record: > type=FANOTIFY msg=audit(1659730979.839:284): resp=1 fan_type=0 > fan_info=3F > > Suggested-by: Paul Moore <paul(a)paul-moore.com&gt; > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > --- > kernel/auditsc.c | 28 +++++++++++++++++++++------- > 1 file changed, 21 insertions(+), 7 deletions(-) > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c > index f000fec52360..0f747015c577 100644 > --- a/kernel/auditsc.c > +++ b/kernel/auditsc.c > @@ -2908,22 +2908,36 @@ void __audit_fanotify(u32 response, size_t len, > char *buf) > > if (!(len && buf)) { > audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY, > - "resp=%u fan_type=0 fan_info=?", response); > + "resp=%u fan_type=0 fan_info=3F", response); /* "?" */ > return; > } > while (c >= sizeof(struct fanotify_response_info_header)) { > + struct audit_context *ctx = audit_context(); > + struct audit_buffer *ab; > + > 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); > + ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_FANOTIFY); > + if (ab) { > + audit_log_format(ab, "resp=%u fan_type=%u fan_info=", > + response, friar->hdr.type); > +#define INCOMPLETE "(incomplete)" > + audit_log_n_hex(ab, INCOMPLETE, sizeof(INCOMPLETE)); > + audit_log_end(ab); > + } > return; > } > - audit_log(audit_context(), GFP_KERNEL, AUDIT_FANOTIFY, > - "resp=%u fan_type=%u fan_info=%u", > - response, friar->hdr.type, friar->audit_rule); > + ab = audit_log_start(ctx, GFP_KERNEL, AUDIT_FANOTIFY); > + if (ab) { > + audit_log_format(ab, "resp=%u fan_type=%u fan_info=", > + response, friar->hdr.type); > + audit_log_n_hex(ab, (char *)&friar->audit_rule, > + sizeof(friar->audit_rule)); One thing to point out, the structure has a member audit_rule. It is probably better to call it rule_number. This is because it has nothing to do with any actual audit rule. It is a rule number meant to be recorded by the audit system. Also, that member is a __u32 type. Hex encoding that directly gives back a __u32 when decoded - which is a bit unexpected since everything else is strings. It would be better to convert the u32 to a base 10 string and then hex encode that. A buffer of 12 bytes should be sufficient.

Thanks, -Steve > + audit_log_end(ab); > + > + } > } > c -= friar->hdr.len; > ib += friar->hdr.len;