Re: printk()s of user-supplied strings (Re: [PATCH] binfmt_elf.c : the BAD_ADDR macro again)

From: Ernie Petrides
Date: Tue Aug 22 2006 - 16:21:20 EST

On Tuesday, 22-Aug-2006 at 7:7 +0400, Solar Designer wrote:

> On Mon, Aug 21, 2006 at 07:36:01PM -0400, Ernie Petrides wrote:
> > - printk(KERN_ERR "Unable to load interpreter %.128s\n",
> > - elf_interpreter);
> I'd rather have this message rate-limited, not dropped completely.

I consider any printk() that can be arbitrarily triggered by an
unprivileged user to be inappropriate, rate-limited or not. I
recommend that it be removed entirely.

> Another long-time concern that I had is that we've got some printk()s
> of user-supplied string data. What about embedded linefeeds - can this
> be used to produce fake kernel messages with arbitrary log level (syslog
> priority)? It certainly seems so.
> Also, there are terminal controls...

These are valid concerns. Allowing the kernel to print user-fabricated
strings is a terrible idea.

Cheers. -ernie
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