netdev - RE: [PATCH V11 3/5] printk: hash addresses printed with %p

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <e8dd4332196348df8938a1ad8991dc84@AcuMS.aculab.com>
Date:   Wed, 6 Dec 2017 10:31:15 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'David Miller' <davem@...emloft.net>,
        "geert@...ux-m68k.org" <geert@...ux-m68k.org>
CC:     "me@...in.cc" <me@...in.cc>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "Jason@...c4.com" <Jason@...c4.com>,
        "tytso@....edu" <tytso@....edu>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "tycho@...ho.ws" <tycho@...ho.ws>,
        "william.c.roberts@...el.com" <william.c.roberts@...el.com>,
        "tj@...nel.org" <tj@...nel.org>,
        "Golden_Miller83@...tonmail.ch" <Golden_Miller83@...tonmail.ch>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "pmladek@...e.com" <pmladek@...e.com>,
        "joe@...ches.com" <joe@...ches.com>,
        "ijc@...lion.org.uk" <ijc@...lion.org.uk>,
        "sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "wilal.deacon@....com" <wilal.deacon@....com>,
        "rostedt@...dmis.org" <rostedt@...dmis.org>,
        "cfries@...gle.com" <cfries@...gle.com>,
        "olorin@...gle.com" <olorin@...gle.com>,
        "danielmicay@...il.com" <danielmicay@...il.com>,
        "tixxdz@...il.com" <tixxdz@...il.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "sfr@...b.auug.org.au" <sfr@...b.auug.org.au>,
        "aryabinin@...tuozzo.com" <aryabinin@...tuozzo.com>,
        "glider@...gle.com" <glider@...gle.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sergei.shtylyov@...entembedded.com" 
        <sergei.shtylyov@...entembedded.com>
Subject: RE: [PATCH V11 3/5] printk: hash addresses printed with %p

From: David Miller
> Sent: 05 December 2017 20:31
...
> > Would it make sense to keep the 3 lowest bits of the address?
> >
> > Currently printed pointers no longer have any correlation with the actual
> > alignment in memory of the object, which is a typical cause of a class of bugs.
> 
> Yeah, this is driving people nuts who wonder why pointers are aligned
> all weird now.

I can also image issues where you want to know whether 2 pointers point
into the same structure (like an skb).
Useful if you suspect that code is using a stale pointer because the
skb got reallocated by some internal function.
I'm not sure such pointers are printed by default though.

I know I have debugged things that required hexdumps of memory areas
referenced by traced pointers.
I won't have done that for anything written with the kernel printf because
getting any more info for a linux kernel oops is actually quite hard.

	David