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From: Josef Bacik <josef@toxicpanda.com>
To: Omar Sandoval <osandov@osandov.com>,
	linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org,
	Al Viro <viro@zeniv.linux.org.uk>,
	Christoph Hellwig <hch@infradead.org>
Cc: Dave Chinner <david@fromorbit.com>, Jann Horn <jannh@google.com>,
	Amir Goldstein <amir73il@gmail.com>,
	Aleksa Sarai <cyphar@cyphar.com>,
	linux-api@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v5 2/9] fs: add O_ALLOW_ENCODED open flag
Date: Mon, 24 Aug 2020 14:28:39 -0400	[thread overview]
Message-ID: <3c44cdf2-e0fd-cea1-4028-d6315ba3b7fd@toxicpanda.com> (raw)
In-Reply-To: <f0db9f271dbe563d2ceaae68f8b74ce4b424efe5.1597993855.git.osandov@osandov.com>

On 8/21/20 3:38 AM, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> The upcoming RWF_ENCODED operation introduces some security concerns:
> 
> 1. Compressed writes will pass arbitrary data to decompression
>     algorithms in the kernel.
> 2. Compressed reads can leak truncated/hole punched data.
> 
> Therefore, we need to require privilege for RWF_ENCODED. It's not
> possible to do the permissions checks at the time of the read or write
> because, e.g., io_uring submits IO from a worker thread. So, add an open
> flag which requires CAP_SYS_ADMIN. It can also be set and cleared with
> fcntl(). The flag is not cleared in any way on fork or exec; it should
> probably be used with O_CLOEXEC in most cases.
> 
> Note that the usual issue that unknown open flags are ignored doesn't
> really matter for O_ALLOW_ENCODED; if the kernel doesn't support
> O_ALLOW_ENCODED, then it doesn't support RWF_ENCODED, either.

It seemed like you agreed to require O_CLOEXEC to be set when using 
O_ALLOW_ENCODED in your last go around, what happened to that?  I know I'd feel 
better if we had that requirement, and if we aren't I'd like to know why we 
can't.  Thanks,

Josef

  reply	other threads:[~2020-08-24 18:28 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21  7:38 [PATCH v5 0/9] fs: interface for directly reading/writing compressed data Omar Sandoval
2020-08-21  7:38 ` [PATCH man-pages v5] Document encoded I/O Omar Sandoval
2020-08-21  9:24   ` Amir Goldstein
2020-08-24 18:15     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 1/9] iov_iter: add copy_struct_from_iter() Omar Sandoval
2020-08-24 18:52   ` Josef Bacik
2020-08-24 21:09     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 2/9] fs: add O_ALLOW_ENCODED open flag Omar Sandoval
2020-08-24 18:28   ` Josef Bacik [this message]
2020-08-24 21:11     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 3/9] fs: add RWF_ENCODED for reading/writing compressed data Omar Sandoval
2020-08-21  8:47   ` Amir Goldstein
2020-08-24 23:49     ` Omar Sandoval
2020-08-25  8:25       ` Amir Goldstein
2020-08-25 17:20         ` Omar Sandoval
2020-08-24 19:07   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 4/9] btrfs: don't advance offset for compressed bios in btrfs_csum_one_bio() Omar Sandoval
2020-08-24 19:17   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 5/9] btrfs: add ram_bytes and offset to btrfs_ordered_extent Omar Sandoval
2020-08-24 19:23   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 6/9] btrfs: support different disk extent size for delalloc Omar Sandoval
2020-08-24 19:26   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 7/9] btrfs: optionally extend i_size in cow_file_range_inline() Omar Sandoval
2020-08-24 19:33   ` Josef Bacik
2020-08-21  7:38 ` [PATCH v5 8/9] btrfs: implement RWF_ENCODED reads Omar Sandoval
2020-08-24 19:54   ` Josef Bacik
2020-08-24 21:23     ` Omar Sandoval
2020-08-21  7:38 ` [PATCH v5 9/9] btrfs: implement RWF_ENCODED writes Omar Sandoval
2020-08-24 20:30   ` Josef Bacik
2020-08-24 21:30     ` Omar Sandoval

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