Re: [PATCH] tracing: Warn when an event dereferences a pointer in TP_printk()

[Vinod Koul]

On 30-06-26, 18:48, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@xxxxxxxxxxx>
> 
> Currently on boot up and when modules are loaded, the trace event
> infrastructure will examine the TP_printk's of every event looking to see
> if it dereferences pointers on the ring buffer via printk formats like
> "%pB" and such. What it doesn't do is check if the arguments themselves
> do a dereference from a pointer.
> 
> This was brought with a fix[1] to the fsl_edma event that had in the
> arguments of the TP_printk(): "__entry->edma->membase"
> 
> The __entry->edma is a pointer saved in the ring buffer. The dereference
> from TP_printk() happens when the user reads the "trace" file which can be
> seconds, minutes, hours, days, weeks, or even months later! There is no
> guarantee that the __entry->edma pointer will still be pointing to what it
> was when it was recorded, and could crash the kernel when a user reads the
> event.
> 
> Add logic to the test_event_printk() that also checks for this case and
> warn if the event dereferences a pointer from the ring buffer.

Reviewed-by: Vinod Koul <vkoul@xxxxxxxxxx>

-- 
~Vinod