lkml.org 
[lkml]   [2012]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: suppress page allocation failure warnings from sys_listxattr
On Tue, Mar 27, 2012 at 03:51:49PM -0700, Andrew Morton wrote:
> On Tue, 13 Mar 2012 14:22:20 -0400
> Dave Jones <davej@redhat.com> wrote:
>
> > This size is user controllable, and so it's trivial for someone to trigger a
> > stream of order:4 page allocation errors.
> >
> > Signed-off-by: Dave Jones <davej@redhat.com>
> >
> > ---
> > There's also a similar problem in setxattr, but I'm not sure how we want
> > to pass NOWARN down to memdup_user. Thoughts ?
> >
> > diff --git a/fs/xattr.c b/fs/xattr.c
> > index 82f4337..544df90 100644
> > --- a/fs/xattr.c
> > +++ b/fs/xattr.c
> > @@ -496,7 +496,7 @@ listxattr(struct dentry *d, char __user *list, size_t size)
> > if (size) {
> > if (size > XATTR_LIST_MAX)
> > size = XATTR_LIST_MAX;
> > - klist = kmalloc(size, GFP_KERNEL);
> > + klist = kmalloc(size, __GFP_NOWARN | GFP_KERNEL);
> > if (!klist)
> > return -ENOMEM;
> > }
>
> hm. The patch is good, but one would hope that it isn't "trivial" to
> trigger a page allocation failure for a kmalloc(65536, GFP_KERNEL) -
> the VM is supposed to be able to handle that.
>
> Is it really *that* easy, or is Something Unusual happening with that
> machine?

Well, the unusual thing was that I was fuzzing system calls for a few hours.

My fuzzing tool was able to trigger these very easily after an hour or two
of uptime and memory had fragmented a little, so yeah, quite trivial.

Dave


\
 
 \ /
  Last update: 2012-03-28 02:19    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site