From: "Theodore Ts'o" <tytso@mit.edu>
To: Dave Chinner <david@fromorbit.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
John Hubbard <jhubbard@nvidia.com>,
Lee Jones <lee.jones@linaro.org>,
linux-ext4@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
Dave Chinner <dchinner@redhat.com>,
Goldwyn Rodrigues <rgoldwyn@suse.com>,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Bob Peterson <rpeterso@redhat.com>,
Damien Le Moal <damien.lemoal@wdc.com>,
Andreas Gruenbacher <agruenba@redhat.com>,
Ritesh Harjani <riteshh@linux.ibm.com>,
Johannes Thumshirn <jth@kernel.org>,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
cluster-devel@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers()
Date: Wed, 23 Feb 2022 22:50:09 -0500 [thread overview]
Message-ID: <YhcAcfY1pZTl3sId@mit.edu> (raw)
In-Reply-To: <20220224014842.GM59715@dread.disaster.area>
On Thu, Feb 24, 2022 at 12:48:42PM +1100, Dave Chinner wrote:
> > Fair enough; on the other hand, we could also view this as making ext4
> > more robust against buggy code in other subsystems, and while other
> > file systems may be losing user data if they are actually trying to do
> > remote memory access to file-backed memory, apparently other file
> > systems aren't noticing and so they're not crashing.
>
> Oh, we've noticed them, no question about that. We've got bug
> reports going back years for systems being crashed, triggering BUGs
> and/or corrupting data on both XFS and ext4 filesystems due to users
> trying to run RDMA applications with file backed pages.
Is this issue causing XFS to crash? I didn't know that.
I tried the Syzbot reproducer with XFS mounted, and it didn't trigger
any crashes. I'm sure data was getting corrupted, but I figured I
should bring ext4 to the XFS level of "at least we're not reliably
killing the kernel".
On ext4, an unprivileged process can use process_vm_writev(2) to crash
the system. I don't know how quickly we can get a fix into mm/gup.c,
but if some other kernel path tries calling set_page_dirty() on a
file-backed page without first asking permission from the file system,
it seems to be nice if the file system doesn't BUG() --- as near as I
can tell, xfs isn't crashing in this case, but ext4 is.
- Ted
next prev parent reply other threads:[~2022-02-24 3:50 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-16 16:31 [REPORT] kernel BUG at fs/ext4/inode.c:2620 - page_buffers() Lee Jones
2022-02-18 1:06 ` John Hubbard
2022-02-18 4:08 ` Theodore Ts'o
2022-02-18 6:33 ` John Hubbard
2022-02-23 23:31 ` Theodore Ts'o
2022-02-24 0:44 ` John Hubbard
2022-02-24 4:04 ` Theodore Ts'o
2022-02-18 7:51 ` Greg Kroah-Hartman
2022-02-23 23:35 ` Theodore Ts'o
2022-02-24 1:48 ` Dave Chinner
2022-02-24 3:50 ` Theodore Ts'o [this message]
2022-02-24 10:29 ` Dave Chinner
2022-02-18 2:54 ` Theodore Ts'o
2022-02-18 4:24 ` Matthew Wilcox
2022-02-18 6:03 ` Theodore Ts'o
2022-02-25 19:24 ` [PATCH -v2] ext4: don't BUG if kernel subsystems dirty pages without asking ext4 first Theodore Ts'o
2022-02-25 20:51 ` Eric Biggers
2022-02-25 21:08 ` Theodore Ts'o
2022-02-25 21:23 ` [PATCH -v3] " Theodore Ts'o
2022-02-25 21:33 ` John Hubbard
2022-02-25 23:21 ` Theodore Ts'o
2022-02-26 0:41 ` John Hubbard
2022-02-26 1:40 ` Theodore Ts'o
2022-02-26 2:00 ` Theodore Ts'o
2022-02-26 2:55 ` John Hubbard
2022-03-03 4:26 ` [PATCH -v4] " Theodore Ts'o
2022-03-03 8:21 ` Christoph Hellwig
2022-03-03 9:21 ` Lee Jones
2022-03-03 14:38 ` [PATCH -v5] ext4: don't BUG if someone " Theodore Ts'o
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