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:   Tue, 2 Feb 2021 18:26:22 -0800
From:   Suren Baghdasaryan <>
To:     Matthew Wilcox <>
Cc:     Sumit Semwal <>,
        Andrew Morton <>,
        Christoph Hellwig <>,
        Liam Mark <>,
        Laura Abbott <>,
        Brian Starkey <>,
        John Stultz <>,
        Christian König <>,
        Chris Goldsworthy <>,
        Ørjan Eide <>,
        Robin Murphy <>,
        James Jones <>,
        Minchan Kim <>,
        Hridya Valsaraju <>,
        Sandeep Patil <>,
        linux-media <>,
        DRI mailing list <>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <>, linux-mm <>,
        LKML <>,
        kernel-team <>
Subject: Re: [PATCH 1/2] mm: replace BUG_ON in vm_insert_page with a return of
 an error

On Tue, Feb 2, 2021 at 5:55 PM Matthew Wilcox <> wrote:
> On Tue, Feb 02, 2021 at 04:31:33PM -0800, Suren Baghdasaryan wrote:
> > Replace BUG_ON(vma->vm_flags & VM_PFNMAP) in vm_insert_page with
> > WARN_ON_ONCE and returning an error. This is to ensure users of the
> > vm_insert_page that set VM_PFNMAP are notified of the wrong flag usage
> > and get an indication of an error without panicing the kernel.
> > This will help identifying drivers that need to clear VM_PFNMAP before
> > using dmabuf system heap which is moving to use vm_insert_page.
> The system may not _panic_, but it is clearly now _broken_.  The device
> doesn't work, and so the system is useless.  You haven't really improved
> anything here.  Just bloated the kernel with yet another _ONCE variable
> that in a normal system will never ever ever be triggered.

We had a discussion in
about how some DRM drivers set up their VMAs with VM_PFNMAP before
mapping them. We want to use vm_insert_page instead of remap_pfn_range
in the dmabuf heaps so that this memory is visible in PSS. However if
a driver that sets VM_PFNMAP tries to use a dmabuf heap, it will step
into this BUG_ON. We wanted to catch and gradually fix such drivers
but without causing a panic in the process. I hope this clarifies the
reasons why I'm making this change and I'm open to other ideas if they
would address this issue in a better way.

Powered by blists - more mailing lists