linux-kernel - Re: [PATCH] fs: fix NULL dereference due to data race in prepend

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: Windows password security audit tool. GUI, reports in PDF.

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

Date:   Thu, 15 Oct 2020 00:08:58 +0100
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        kernel-team@...com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] fs: fix NULL dereference due to data race in
 prepend_path()

On Wed, Oct 14, 2020 at 02:49:18PM -0700, Linus Torvalds wrote:
> On Wed, Oct 14, 2020 at 2:40 PM Andrii Nakryiko <andrii@...nel.org> wrote:
> >
> > Fix data race in prepend_path() with re-reading mnt->mnt_ns twice without
> > holding the lock. is_mounted() does check for NULL, but is_anon_ns(mnt->mnt_ns)
> > might re-read the pointer again which could be NULL already, if in between
> > reads one of kern_unmount()/kern_unmount_array()/umount_tree() sets mnt->mnt_ns
> > to NULL.
> 
> This seems like the obviously correct fix, so I think I'll just apply
> it directly.
> 
> Al? Holler if you have any issues with this..

See upthread.  If you've already grabbed it, I'll just push a followup cleanup.