linux-kernel - Re: [v4 PATCH 5/6] mm: shmem: don't truncate page if memory failure happens

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:   Wed, 20 Oct 2021 07:30:07 +0900
From:   Naoya Horiguchi <naoya.horiguchi@...ux.dev>
To:     Yang Shi <shy828301@...il.com>
Cc:     HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>, Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Peter Xu <peterx@...hat.com>,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v4 PATCH 5/6] mm: shmem: don't truncate page if memory failure
 happens

On Tue, Oct 19, 2021 at 10:29:51AM -0700, Yang Shi wrote:
> On Mon, Oct 18, 2021 at 10:52 PM Naoya Horiguchi
> <naoya.horiguchi@...ux.dev> wrote:
> >
> > On Thu, Oct 14, 2021 at 12:16:14PM -0700, Yang Shi wrote:
...
> > > @@ -2466,7 +2467,15 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
> > >                       return -EPERM;
> > >       }
> > >
> > > -     return shmem_getpage(inode, index, pagep, SGP_WRITE);
> > > +     ret = shmem_getpage(inode, index, pagep, SGP_WRITE);
> > > +
> > > +     if (*pagep && PageHWPoison(*pagep)) {
> >
> > shmem_getpage() could return with pagep == NULL, so you need check ret first
> > to avoid NULL pointer dereference.
> 
> Realy? IIUC pagep can't be NULL. It is a pointer's pointer passed in
> by the caller, for example, generic_perform_write(). Of course,
> "*pagep" could be NULL.

Oh, I simply missed this. You're right. Please ignore my comment on this.

- Naoya Horiguchi