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  PHC 
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Fri, 20 Nov 2020 13:42:42 -0500
From:   Steven Rostedt <>
To:     Alan Stern <>
Cc:     Petr Mladek <>,
        Sergey Senozhatsky <>,
        Kernel development list <>
Subject: Re: Printk specifiers for __user pointers

On Fri, 20 Nov 2020 11:44:12 -0500
Alan Stern <> wrote:

> To the VSPRINTF maintainers:
> Documentation/core-api/printk-formats.rst lists a large number of format 
> specifiers for pointers of various sorts.  Yet as far as I can see, 
> there is no specifier meant for use with __user pointers.
> The security implications of printing the true, unmangled value of a 
> __user pointer are minimal, since doing so does not leak any kernel 
> information.  So %px would work, but tools like don't like 
> it.
> Should a new specifier be added?  If not, should we simply use %px?

There's currently no user of '%pu' (although there is a '%pus'. Perhaps we
should have a '%pux'?

I would even state that if it is used, that if makes sure that the value is
indeed a user space pointer (goes through the same checks as accessing user
space), before its printed, otherwise it shows "(fault)" or something.

-- Steve

Powered by blists - more mailing lists