linux-kernel - Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid pointers

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20180315080309.GF3628@jagdpanzerIV>
Date:   Thu, 15 Mar 2018 17:03:09 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Tobin C . Harding" <me@...in.cc>, Joe Perches <joe@...ches.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.cz>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v3] vsprintf: Prevent crash when dereferencing invalid
 pointers

On (03/15/18 16:58), Sergey Senozhatsky wrote:
> On (03/14/18 15:09), Petr Mladek wrote:
> [..]
> > +static const char *check_pointer_access(const void *ptr)
> > +{
> > +	unsigned char byte;
> > +
> > +	if (!ptr)
> > +		return "(null)";
> > +
> > +	if (probe_kernel_read(&byte, ptr, 1))
>                                         ^^^^^
> Why one byte? 			     sizeof(ptr)?

I think there is a shorter version - probe_kernel_address(),
which, seems, was designed for this particular kind of stuff.

	void *p;

	if (probe_kernel_address(ptr, p))
		....

	-ss