lkml.org 
[lkml]   [2020]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v7 2/8] fs: Add standard casefolding support
On Mon, Feb 10, 2020 at 03:11:13PM -0800, Daniel Rosenberg wrote:
> On Fri, Feb 7, 2020 at 6:12 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > On Fri, Feb 07, 2020 at 05:35:46PM -0800, Daniel Rosenberg wrote:
> >
> >
> > Again, is that safe in case when the contents of the string str points to
> > keeps changing under you?
>
> I'm not sure what you mean. I thought it was safe to use the str and
> len passed into d_compare. Even if it gets changed under RCU
> conditions I thought there was some code to ensure that the name/len
> pair passed in is consistent, and any other inconsistencies would get
> caught by d_seq later. Are there unsafe code paths that can follow?

If you ever fetch the same byte twice, you might see different values.
You need a fairly careful use of READ_ONCE() or equivalents to make
sure that you don't get screwed over by that.

Sure, ->d_seq mismatch will throw the result out, but you need to make
sure you won't oops/step on uninitialized memory/etc. in process.

It's not impossible to get right, but it's not trivial and you need all
code working with that much more careful than normal for string handling.

\
 
 \ /
  Last update: 2020-02-11 00:43    [W:0.074 / U:5.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site