Re: fs: out of bounds on stack in iov_iter_advance

From	Ross Zwisler <ross.zwisler@linux.intel.com>
Newsgroups	linux.kernel
Subject	Re: fs: out of bounds on stack in iov_iter_advance
Date	2015-10-18 06:20 +0200
Message-ID	<qkNBV-2kG-45@gated-at.bofh.it> (permalink)
References	(2 earlier) <pYoKd-2ZR-15@gated-at.bofh.it> <pZ4q6-59O-5@gated-at.bofh.it> <q9TAZ-5YM-1@gated-at.bofh.it> <qexgt-oR-1@gated-at.bofh.it> <qkFl0-6VB-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Sat, Oct 17, 2015 at 03:22:19PM -0400, Sasha Levin wrote:
> On 09/30/2015 05:30 PM, Sasha Levin wrote:
> > On 09/17/2015 10:24 PM, Sasha Levin wrote:
> >> On 08/19/2015 01:46 AM, Al Viro wrote:
> >>>> or mapping->a_ops->direct_IO() returned more
> >>>>> than 'count'.
> >>> 	Was there DAX involved?  ->direct_IO() in there is blkdev_direct_IO(),
> >>> which takes rather different paths in those cases...
> >>>
> >>
> >> So I've traced this all the way back to dax_io(). I can trigger this with:
> >>
> >> diff --git a/fs/dax.c b/fs/dax.c
> >> index 93bf2f9..2cdb8a5 100644
> >> --- a/fs/dax.c
> >> +++ b/fs/dax.c
> >> @@ -178,6 +178,7 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
> >>         if (need_wmb)
> >>                 wmb_pmem();
> >>
> >> +       WARN_ON((pos == start) && (pos - start > iov_iter_count(iter)));
> >>         return (pos == start) ? retval : pos - start;
> >>  }
> >>
> >> So it seems that iter gets moved twice here: once in dax_io(), and once again
> >> back at generic_file_read_iter().
> >>
> >> I don't see how it ever worked. Am I missing something?
> > 
> > Ping?
> 
> Ping?

I'll try and find time to look at this issue this week.  Sasha, do you have a
more targeted reproducer, or is still just the trinity fuzzer?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Thread

Re: fs: out of bounds on stack in iov_iter_advance Sasha Levin <sasha.levin@oracle.com> - 2015-10-17 21:30 +0200
  Re: fs: out of bounds on stack in iov_iter_advance Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-10-18 06:20 +0200
    Re: fs: out of bounds on stack in iov_iter_advance Sasha Levin <sasha.levin@oracle.com> - 2015-10-20 01:40 +0200

csiph-web