Date: Tue, 28 Nov 2017 10:12:09 +0000 From: David Laight <David.Laight@...LAB.COM> To: "'Eric W. Biederman'" <ebiederm@...ssion.com>, Linus Torvalds <torvalds@...ux-foundation.org> CC: "Tobin C. Harding" <me@...in.cc>, "Jason A. Donenfeld" <Jason@...c4.com>, Theodore Ts'o <tytso@....edu>, Kees Cook <keescook@...omium.org>, "Paolo Bonzini" <pbonzini@...hat.com>, Tycho Andersen <tycho@...ho.ws>, "Roberts, William C" <william.c.roberts@...el.com>, Tejun Heo <tj@...nel.org>, "Jordan Glover" <Golden_Miller83@...tonmail.ch>, 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>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <wilal.deacon@....com>, Steven Rostedt <rostedt@...dmis.org>, Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>, Daniel Micay <danielmicay@...il.com>, Djalal Harouni <tixxdz@...il.com>, Radim Krcmár <rkrcmar@...hat.com>, "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>, KVM list <kvm@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com> Subject: RE: [PATCH 0/5] add printk specifier %px, unique identifier From: Eric W. Biederman > Sent: 28 November 2017 06:27 > Linus Torvalds <torvalds@...ux-foundation.org> writes: > > > On Mon, Nov 27, 2017 at 4:03 PM, Linus Torvalds > > <torvalds@...ux-foundation.org> wrote: > >> > >> So the big remaining ones for me are the /proc/<pid>/stack (stack > >> pointers) and the /proc/net/* ones. > >> > >> I'm a bit disappointed that those haven't been fixed already and > >> aren't even in this series.. > > > > Oh well, I just did /proc/<pid>/stack by making it just print 0 > > unconditionally rather than the hex number. > > Patch? > > I know I have used /proc/<pid>/stack manually many times when looking > at a system where something is hung/weird and I needed to see what is > going on. The backtrace inside the kernel can be invaluable. Ditto - after I spotted it. Also the similar tracebacks from echo t >/proc/sysrq-trigger although they are less useful unless you've a big kernel message buffer. Although they can be requested from a keyboard if everything except the keyboard interrupt is borked. > At the same time I don't know if we actually need the hex address. > But please don't break that interface it is very useful. Definitely need to know which addresses are zero (or near zero). I will have tied the addresses there to ones available elsewhere. (In private trace that won't be affected by whatever kernel printf does with %p.) If you want to hide addresses, then maybe use a write-only sysctl. David
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