From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 053B4C55171 for ; Sat, 1 Aug 2026 00:47:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.sourceforge.net; s=beta; h=Content-Transfer-Encoding:Content-Type:Cc: List-Subscribe:List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: Subject:In-Reply-To:MIME-Version:References:Message-ID:To:From:Date:Sender: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=C2fc7TaaCW6IXFJRBPXlDFSaaBjF+ws1LfDw9cswmAk=; b=jHBem2RZhHOkdfDxE/7rFqjl8N vsouFry9ZZGuKRBz4wTi7Xg4zMkUh8ygpvFAkcZvI3T4q/jvepf+kLGNi2px70PFk5zGyTi5Ervm4 LTh43xHfnTlQT03sUbgSh+21tn2Gjy2G8QNMosh2aSbdJ3/Lo8GtC7KzYh4Flgt2FXok=; Received: from [127.0.0.1] (helo=sfs-ml-1.v29.lw.sourceforge.com) by sfs-ml-1.v29.lw.sourceforge.com with esmtp (Exim 4.95) (envelope-from ) id 1wpxse-0000Kf-BH; Sat, 01 Aug 2026 00:47:09 +0000 Received: from [172.30.29.66] (helo=mx.sourceforge.net) by sfs-ml-1.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.95) (envelope-from ) id 1wpxsc-0000KX-CK for linux-f2fs-devel@lists.sourceforge.net; Sat, 01 Aug 2026 00:47:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=gMek1aawQ8IyooAOw8hjJzP++g15hi+kUNuEx4O2XuA=; b=cvfklL6Mgf6gXdSQyJLnwKGWc/ aRRqXg+4hTf0Vv/hVfOQVjD+mtJdkiNI91qcCiEdmteEGDf4oq048rTs+YQW01PxX2PgUiqAyKYD+ MqTyWl0cgHlCnT6tGTrlQOFomDoxc6i1uhISZcSf7PWytCOsMyI7dlQ6XOPMMpTbbQ3w=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=gMek1aawQ8IyooAOw8hjJzP++g15hi+kUNuEx4O2XuA=; b=WmCPVRAs0C5FtywLvVYRhAM+Xa Z+trOKeGVdLB9rACYx8LlYrfR5nN+AFBLfB5hgR0NYxe5AtprsLsC03AGtKCq+YyrH8g1jXso6tdY a5/vSCAlo7GY3q5ZMP4Be4oRweOh+H+Tqhr7648GmzrDH5GCMBbMBPRvAVj2kbhGfBdM=; Received: from out-170.mta0.migadu.com ([91.218.175.170]) by sfi-mx-1.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.95) id 1wpxsb-00012A-Kb for linux-f2fs-devel@lists.sourceforge.net; Sat, 01 Aug 2026 00:47:07 +0000 Date: Sat, 1 Aug 2026 08:46:52 +0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1785545219; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gMek1aawQ8IyooAOw8hjJzP++g15hi+kUNuEx4O2XuA=; b=Lp/5WC0ukjnAn5o7N1qqH1jN1lRSaj6RecCQ9ONDeU+uZ3dm1b6L3FalP3D7qZ6EHAhVdC VlIh6gP28hAflRVDqF1Bq042TiBVII/vlLXde6jAxOk4MqdsHPCkYT7WPSTm3YwOPD+5px ZYNtt22HoOYMfrGxy6XWPDx99Au6IY4= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Baoquan He To: Eric Biggers Message-ID: References: <20260730184853.48347-1-ebiggers@kernel.org> <20260731181408.GA12803@sol> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20260731181408.GA12803@sol> X-Migadu-Flow: FLOW_OUT X-Headers-End: 1wpxsb-00012A-Kb Subject: Re: [f2fs-dev] [PATCH] mm/swap: reject swapon() on filesystem-level encrypted files X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Barry Song , Kairui Song , Nhat Pham , Chris Li , Youngjun Park , Kemeng Shi , linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org, linux-fscrypt@vger.kernel.org, Andrew Morton , linux-ext4@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 07/31/26 at 11:14am, Eric Biggers wrote: > On Fri, Jul 31, 2026 at 11:11:02PM +0800, Baoquan He wrote: > > On 07/30/26 at 11:48am, Eric Biggers wrote: > > > 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. > > > > > > Fixes: 9bd8212f981e ("ext4 crypto: add encryption policy and password salt support") > > > Fixes: f424f664f0e8 ("f2fs crypto: add encryption policy and password salt support") > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Eric Biggers > > > --- > > > Documentation/filesystems/fscrypt.rst | 4 ++++ > > > mm/swapfile.c | 4 ++++ > > > 2 files changed, 8 insertions(+) > > > > > > diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst > > > index c0dd35f1af12..cba1989777da 100644 > > > --- a/Documentation/filesystems/fscrypt.rst > > > +++ b/Documentation/filesystems/fscrypt.rst > > > @@ -1238,6 +1238,10 @@ astute users may notice some differences in behavior: > > > > > > - DAX (Direct Access) is not supported on encrypted files. > > > > > > +- Encrypted files cannot be used directly as swap files. To swap to > > > + an encrypted file, set up a loopback device on top of it. > > > + Alternatively, encrypted swap can use a dm-crypt device instead. > > > + > > > - The maximum length of an encrypted symlink is 2 bytes shorter than > > > the maximum length of an unencrypted symlink. For example, on an > > > EXT4 filesystem with a 4K block size, unencrypted symlinks can be up > > > diff --git a/mm/swapfile.c b/mm/swapfile.c > > > index 78b49b0658ad..e4991da81b5f 100644 > > > --- a/mm/swapfile.c > > > +++ b/mm/swapfile.c > > > @@ -3650,6 +3650,10 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) > > > error = -EBUSY; > > > goto bad_swap_unlock_inode; > > > } > > > + if (IS_ENCRYPTED(inode)) { > > > + error = -EINVAL; > > > + goto bad_swap_unlock_inode; > > > + } > > > > Sounds reasonable to me. > > > > One minor suggestion: it might be helpful to emit a pr_warn_once() > > explaining *why* the swapon was rejected and pointing users to the > > dm-crypt / loopback alternatives, so the -EINVAL isn't opaque. > > Optional though -- the check itself is what matters. > > How's this? > > pr_warn_once("Filesystem-level encrypted swapfile '%s' is unsupported. Create a loop device over it, or use dm-crypt\n", name->name); Looks good to me, thx. > > > And this patch updates fscrypt.rst. Would it be good to also > > update the swapon(8) man page to document the new -EINVAL > > condition? > > > > Other than these, > > > > Reviewed-by: Baoquan He > > swapon(8) is for the util-linux program, not the syscall, so it doesn't > document error codes specifically. It does have a NOTES section that > incompletely documents filesystem-specific constraints on swap files. > It's missing most of the current constraints. But sure, I'll send a > patch that adds a note to there about this one. That will be a > util-linux patch. Sounds great, thanks. _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel