Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, 4 Apr 2018 12:04:42 -0700 Linus Torvalds wrote: > > So at the *very* least this would need to be percpu logic, but even > that is honestly broken since an NMI might come in and want to printk > too. > > Why don't you just use %px? That avoids all of

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, 4 Apr 2018 12:04:42 -0700 Linus Torvalds wrote: > > So at the *very* least this would need to be percpu logic, but even > that is honestly broken since an NMI might come in and want to printk > too. > > Why don't you just use %px? That avoids all of these hacks. Just need to remember

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, Apr 4, 2018 at 10:13 AM, Steven Rostedt wrote: > > Something like this will even prevent modules from disabling the printk > hash... That still seems broken. The *natural* thing to do would seem to be to tie the hash to the printk state, kind of like the percpu

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, Apr 4, 2018 at 10:13 AM, Steven Rostedt wrote: > > Something like this will even prevent modules from disabling the printk > hash... That still seems broken. The *natural* thing to do would seem to be to tie the hash to the printk state, kind of like the percpu buffers that

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, 4 Apr 2018 11:34:55 +0900 Sergey Senozhatsky wrote: > On (04/03/18 18:03), Steven Rostedt wrote: > > > > > he'd want you to change all the trace_printk()s to %px with > > > justifications, though. > > > > What trace_printk()s do you want to

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Wed, 4 Apr 2018 11:34:55 +0900 Sergey Senozhatsky wrote: > On (04/03/18 18:03), Steven Rostedt wrote: > > > > > he'd want you to change all the trace_printk()s to %px with > > > justifications, though. > > > > What trace_printk()s do you want to change? They are throw away > >

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On (04/03/18 18:03), Steven Rostedt wrote: > > > he'd want you to change all the trace_printk()s to %px with > > justifications, though. > > What trace_printk()s do you want to change? They are throw away > functions. trace_printk() is not something that stays in the kernel. > It's added during

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On (04/03/18 18:03), Steven Rostedt wrote: > > > he'd want you to change all the trace_printk()s to %px with > > justifications, though. > > What trace_printk()s do you want to change? They are throw away > functions. trace_printk() is not something that stays in the kernel. > It's added during

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Tue, 3 Apr 2018 14:43:43 -0700 Kees Cook wrote: > > A static_key is added called "trace_debug" and if it is set, then %p will > > not be hashed. > > Hrm, well, using a static key does make it weirder for an attacker to enable. > :) Not just weirder, much more

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Tue, 3 Apr 2018 14:43:43 -0700 Kees Cook wrote: > > A static_key is added called "trace_debug" and if it is set, then %p will > > not be hashed. > > Hrm, well, using a static key does make it weirder for an attacker to enable. > :) Not just weirder, much more difficult. static_keys are

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Tue, Apr 3, 2018 at 2:31 PM, Steven Rostedt wrote: > From: Steven Rostedt (VMware) > > While debugging an issue I needed to see if the pointers were being > processed correctly with trace_printk() and after using "%p" and > triggering my bug and trace

Re: [PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

On Tue, Apr 3, 2018 at 2:31 PM, Steven Rostedt wrote: > From: Steven Rostedt (VMware) > > While debugging an issue I needed to see if the pointers were being > processed correctly with trace_printk() and after using "%p" and > triggering my bug and trace output, I was disappointed that all my >

[PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

From: Steven Rostedt (VMware) While debugging an issue I needed to see if the pointers were being processed correctly with trace_printk() and after using "%p" and triggering my bug and trace output, I was disappointed that all my pointers were random garbage and didn't

[PATCH v2] tracing, printk: Force no hashing when trace_printk() is used

From: Steven Rostedt (VMware) While debugging an issue I needed to see if the pointers were being processed correctly with trace_printk() and after using "%p" and triggering my bug and trace output, I was disappointed that all my pointers were random garbage and didn't produce anything useful