[lkml]   [2014]   [Apr]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [patch 2/2] lib/string.c: strlcpy() might read too far
On Wed, 2 Apr 2014 11:47:31 +0300 Dan Carpenter <> wrote:

> Imagine you have a user controlled variable at the end of a struct which
> is allocated at the end of a page. The strlen() could read beyond the
> mapped memory and cause an oops.

Well, it's hard to conceive of a situation where anything like this
could happen. Code which copies a string from userspace should
immediately ensure that the kernel copy is null-terminated. But... I
guess it's defense in depth.

> Probably there are two reasons why we have never hit this condition in
> real life. First you would have to be really unlucky for all the
> variables to line up so the oops can happen. Second we don't do a lot
> of fuzzing with invalid strings.
> The strnlen() call is obviously a little bit slower than strlen() but I
> have tested it and I think it's probably ok.

If we cared about speed we wouldn't take two passes across the input
string ;)

 \ /
  Last update: 2014-04-15 01:01    [W:0.076 / U:31.548 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site