Eric Biggers da45847766 mm/swap: reject swapon() on filesystem-level encrypted files
commit c310a8932a upstream.

ext4 and f2fs don't prevent filesystem-level encrypted files from being
set up directly as swap files.  In this case, encryption is bypassed.

No one should be doing this, vs.  the methods of encrypted swap that
actually do work (such as swapping to a dm-crypt device, or swapping to a
loopback device on top of a filesystem-level encrypted file).

Nevertheless, to prevent user error, make swapon() explicitly reject this
case.  Document this behavior in fscrypt.rst as well.

Link: https://lore.kernel.org/20260803180426.3123-1-ebiggers@kernel.org
Fixes: 9bd8212f98 ("ext4 crypto: add encryption policy and password salt support")
Fixes: f424f664f0 ("f2fs crypto: add encryption policy and password salt support")
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: Baoquan He <baoquan.he@linux.dev>
Reviewed-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2026-09-02 14:29:20 +02:00
2026-05-23 13:03:09 +02:00
2026-08-03 11:15:40 +02:00
2026-05-23 13:03:09 +02:00
2026-08-28 08:21:42 +02:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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