Re: [PATCH 1/6] serial: sh-sci: Reveal ptrval in dev_dbg

From: Simon Horman
Date: Mon May 06 2019 - 09:47:54 EST

On Sat, May 04, 2019 at 02:42:53AM +0200, Eugeniu Rosca wrote:
> Starting with v4.15-rc2 commit ad67b74d2469d9 ("printk: hash addresses
> printed with %p"), enabling debug prints in sh-sci.c would generate
> output like below confusing the users who try to sneak into the
> internals of the driver:
> sh-sci e6e88000.serial: sci_request_dma: TX: got channel (____ptrval____)
> sh-sci e6e88000.serial: sci_request_dma: mapped 4096@(____ptrval____) to 0x00000006798bf000
> sh-sci e6e88000.serial: sci_request_dma: RX: got channel (____ptrval____)
> sh-sci e6e88000.serial: sci_dma_tx_work_fn: (____ptrval____): 0...2, cookie 2
> There are two possible fixes for that:
> - get rid of '%p' prints if they don't reveal any useful information
> - s/%p/%px/, since it is unlikely we have any concerns leaking the
> pointer values when running a debug/non-production kernel

I am concerned that this may expose information in circumstances
where it is undesirable. Is it generally accepted practice to
use %px in conjunction with dev_dbg() ?