linux-kernel - Re: [PATCH v4 4/4] fanotify,audit: deliver fan

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Date:   Wed, 10 Aug 2022 15:15:21 -0400
From:   Steve Grubb <sgrubb@...hat.com>
To:     Linux-Audit Mailing List <linux-audit@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org, Richard Guy Briggs <rgb@...hat.com>
Cc:     Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...isplace.org>,
        Richard Guy Briggs <rgb@...hat.com>, Jan Kara <jack@...e.cz>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH v4 4/4] fanotify,audit: deliver fan_info as a hex-encoded string

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@...l-moore.com>
> Signed-off-by: Richard Guy Briggs <rgb@...hat.com>
> ---
>  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;