Re: [PATCH] RFC: selinux avc trace

[Steven Rostedt]

On Thu, 30 Jul 2020 16:29:12 +0200
peter enderborg <peter.enderborg@xxxxxxxx> wrote:

> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM avc
> +
> +#if !defined(_TRACE_AVC_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_AVC_H
> +
> +#include <linux/tracepoint.h>
> +TRACE_EVENT(avc_data,
> +ÂÂÂ ÂÂÂ TP_PROTO(u32 requested,
> +ÂÂÂ ÂÂÂ ÂÂÂÂ u32 denied,
> +ÂÂÂ ÂÂÂ ÂÂÂÂ u32 audited,
> +ÂÂÂ ÂÂÂ ÂÂÂÂ int result,
> +ÂÂÂ ÂÂÂ ÂÂÂÂ const char *msg
> +ÂÂÂ ÂÂÂ ÂÂÂÂ ),
> +
> +ÂÂÂ ÂÂÂ TP_ARGS(requested, denied, audited, result,msg),
> +
> +ÂÂÂ ÂÂÂ TP_STRUCT__entry(
> +ÂÂÂ ÂÂÂ ÂÂÂ Â__field(u32, requested)
> +ÂÂÂ ÂÂÂ ÂÂÂ Â__field(u32, denied)
> +ÂÂÂ ÂÂÂ ÂÂÂ Â__field(u32, audited)
> +ÂÂÂ ÂÂÂ ÂÂÂ Â__field(int, result)
> +ÂÂÂ ÂÂÂ ÂÂÂ Â__array(char, msg, 255)

You want to use __string() here, otherwise you are wasting a lot of
buffer space.

		__string( msg, msg)

> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂÂÂ ),
> +
> +ÂÂÂ ÂÂÂ TP_fast_assign(
> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂ __entry->requestedÂÂÂ = requested;
> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂ __entry->deniedÂÂÂ = denied;
> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂ __entry->auditedÂÂÂ = audited;
> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂ __entry->resultÂÂÂ = result;
> +ÂÂÂ ÂÂÂ ÂÂÂ ÂÂ memcpy(__entry->msg, msg, 255);

Not to mention, the above is a bug. As the msg being passed in, is
highly unlikely to be 255 bytes. You just leaked all that memory after
the sting to user space.

Where you want here:

		__assign_str( msg, msg );


-- Steve



> +ÂÂÂ ),
> +
> +ÂÂÂ ÂÂÂ TP_printk("requested=0x%x denied=%d audited=%d result=%d
> msg=%s",
> +ÂÂÂ ÂÂÂ ÂÂÂÂÂ __entry->requested, __entry->denied, __entry->audited,
> __entry->result, __entry->msg
> +ÂÂÂ ÂÂÂ ÂÂÂÂÂ )