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

From: Steve Grubb
Date: Wed Aug 10 2022 - 15:15:56 EST


Hell Richard,

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

I compiled a new kernel and run old user space on this. The above event is
exactly what I see in my audit logs. Why the fan_info=3F? I really would have
expected 0. What if the actual rule number was 63? I think this will work
better to leave everything 0 with old user space.

-Steve

> Suggested-by: Paul Moore <paul@xxxxxxxxxxxxxx>
> Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> ---
> 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));
> + audit_log_end(ab);
> +
> + }
> }
> c -= friar->hdr.len;
> ib += friar->hdr.len;