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Date: Wed, 4 Oct 2017 12:23:02 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Jann Horn <jannh@...gle.com>
Cc: Kees Cook <keescook@...omium.org>, "Tobin C. Harding" <me@...in.cc>, 
	Greg KH <gregkh@...uxfoundation.org>, Petr Mladek <pmladek@...e.com>, 
	Joe Perches <joe@...ches.com>, Ian Campbell <ijc@...lion.org.uk>, 
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, LKML <linux-kernel@...r.kernel.org>, 
	Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, William Roberts <william.c.roberts@...el.com>, 
	Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>
Subject: Re: [RFC V2 4/6] lib: vsprintf: default
 kptr_restrict to the maximum value

On Wed, Oct 4, 2017 at 12:13 PM, Jann Horn <jannh@...gle.com> wrote:
>
> Actually, /proc/kallsyms uses %pK, which hacks around this issue
> by checking for `euid != uid` in addition to the capability check - so this
> isn't exploitable through a typical setuid program.

Fair enough, you'd have to be a pretty broken suid program to have set
uid to euid before reading some untrusted file descriptor.

I could still imagine happening (hey, the X server used to sendmsg
file descriptors back and forth), but hopefully it's not really
realistic.

                  Linus

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