From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 118C23BED11; Mon, 27 Jul 2026 20:13:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785183223; cv=none; b=XYPGSEYquHVuxmdvNZFtjhGrLeoWZiYi/b7nbm+4C9u+/bHZP7PGebLmjf2LdJrr2A9FXd832vbLk06hee1/nt3SS2os6+EDjG2TTa5K7By2BPROt1oTpaUlrraYTolcsK+mgmpUwJZkddt5M+cv1nN2cHfPsS4gAfyhrcknIYQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785183223; c=relaxed/simple; bh=JyJajv7ypRVB97a4lg9EHymN1lI1zY4F0HB23gS0iX8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=hfjItsqVZ5KKdNJZRGPTyN9mLPpBaS+n4OXOGQV1AS6HlkRaDkHmY3ccjBVL/R9upiPw3Yf8/DQtoDS5BbKoEwDEs0n1KQhM6eY4LxDC6NUO1nF079O+6491I5xWr7BBZfOnWOTrgBuG6K/O1ATL3OBBxi0TSRcBzGQmnCRm+io= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fsLFXkau; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fsLFXkau" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68E121F000E9; Mon, 27 Jul 2026 20:13:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785183221; bh=U4qhSK5NtkFYAAUbEPeaE20RlHxWcVudd2tKbsEQeyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=fsLFXkaud9Q/caSgsdgHSDv35JXS9fsaDY2XMLDfGTqwSNMibZMLy0zZ0HJaoUORa by8QAccBVJ1cLSrib1a9Uo5N8YUuASuoe7jgcnHjNwDPwGNZcUU+pZ9QSmnoawmMPN ozuYj196tNmMewZj9l1w1eb6Ay8eDnCpILC6XT6Eg8At4SDn7+tI/G+dS8teU9FL5/ QG1jdQlOlUJEV2rksWuyj0GvX5+WVagKO0ZyTevT1oY0J1gF+5mM1nSRDJnRwgLbe5 pczx8S5rPsN1RWFTAB15sbmbdYjX1YogIgSoWN1YrUfdNwWcppUbXy+qeVTK8VY/FC z9bLgPEiDjhJA== Date: Mon, 27 Jul 2026 20:13:39 +0000 From: Eric Biggers To: Jan Kara Cc: Ojaswin Mujoo , linux-ext4@vger.kernel.org, Theodore Ts'o , Ritesh Harjani , Zhang Yi , linux-kernel@vger.kernel.org, Baokun Li , Disha Goel Subject: Re: [PATCH] ext4: turn off DAX on new files when encryption is set Message-ID: <20260727201339.GD1021387@google.com> References: <20260723085648.1500357-1-ojaswin@linux.ibm.com> <20260727194350.GC1021387@google.com> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260727194350.GC1021387@google.com> On Mon, Jul 27, 2026 at 07:43:50PM +0000, Eric Biggers wrote: > On Mon, Jul 27, 2026 at 09:06:23PM +0200, Jan Kara wrote: > > On Thu 23-07-26 14:26:48, Ojaswin Mujoo wrote: > > > Currently, when setting the S_ENCRYPTED flag on a new regular inode in > > > a -o dax=always mounted FS, we seem to be erroneously retaining the S_DAX > > > flag. This is because the newly created inode ends up with the following: > > > > > > __ext4_new_inode() > > > ext4_set_inode_flags(init=true) // sets S_DAX > > > fscrypt_set_context() > > > ext4_set_context() > > > ext4_set_inode_flags(init=false) // sets S_ENCRYPTED but > > > doesn't clears S_DAX > > > ext4_set_aops > > > inode->i_mapping->a_ops = &ext4_dax_aops; > > > > > > Due to the S_DAX flag, the excrypted inode gets ext4_dax_aops and it > > > silently ends up bypassing encryption completely. This is reflected in > > > multiple xfstests failures like generic/548. To fix this, ensure we disable > > > S_DAX correctly when S_ENCRYPTED is being set on a newly created inode. It > > > is safe to change DAX state there because ext4_set_aops() later can > > > correctly detect S_DAX unset and assign the correct aops. > > > > > > The fix was actually the intended behavior however it seemed to have > > > silently changed in 043546e46dc7. > > > > > > Fixes: 043546e46dc7 ("fs/ext4: Only change S_DAX on inode load") > > > Reported-by: Disha Goel > > > Signed-off-by: Ojaswin Mujoo > > > --- > > > fs/ext4/crypto.c | 15 +++++++++++---- > > > fs/ext4/inode.c | 10 ++++++---- > > > 2 files changed, 17 insertions(+), 8 deletions(-) > > > > > > diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c > > > index f41f320f4437..2d409114e02e 100644 > > > --- a/fs/ext4/crypto.c > > > +++ b/fs/ext4/crypto.c > > > @@ -134,6 +134,7 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, > > > { > > > handle_t *handle = fs_data; > > > int res, res2, credits, retries = 0; > > > + bool init = S_ISREG(inode->i_mode); > > > > Hum, I have some comments: IMHO the change is confusing because the meaning > > of 'init' argument of ext4_set_inode_flags() doesn't mean the first setting > > of flags any longer. And the reliance on ext4_set_context() getting called > > in a safe place exactly for regular files is rather subtle as well. > > > > Also does the change to ext4_set_inode_flags() really work? As far as I'm > > reading the ext4 crypto implementation, I don't see where we'd be setting > > EXT4_INODE_ENCRYPT for inodes with already enabled encryption (where we > > load the context from xattrs through ext4_get_context()) and thus DAX would > > still get enabled for such inodes? What am I missing? > > Maybe __ext4_new_inode() should set the encryption flag on the inode > earlier? Currently it decides whether the inode will be encrypted, then > calls ext4_set_inode_flags(), then calls fscrypt_set_context() (and thus > ext4_set_context()). That last step sets the flag and calls > ext4_set_inode_flags() *again*. > > I don't remember if there's a reason for that redundancy, but it might > just be for historical reasons. ext4_set_context() is called in two > different cases: when a new inode is created and it's encrypted from the > beginning, and when FS_IOC_SET_ENCRYPTION_POLICY is executed on an empty > directory. The latter does have to set the encrypt flag there. > > - Eric Here's an idea. I haven't tested it though. Note that this would align ext4 closer with f2fs, which already sets the encrypt flag before it calls fscrypt_set_context(). diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c index f41f320f4437..c4bfe18fd527 100644 --- a/fs/ext4/crypto.c +++ b/fs/ext4/crypto.c @@ -144,7 +144,7 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, if (inode->i_ino == EXT4_ROOT_INO) return -EPERM; - if (WARN_ON_ONCE(IS_DAX(inode) && i_size_read(inode))) + if (WARN_ON_ONCE(IS_DAX(inode))) return -EINVAL; if (ext4_test_inode_flag(inode, EXT4_INODE_DAX)) @@ -163,6 +163,14 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, */ if (handle) { + /* + * ext4 should have set the encrypt flag on the inode already, + * and it should not have enabled inline data. + */ + if (WARN_ON_ONCE(!IS_ENCRYPTED(inode))) + return -EINVAL; + if (WARN_ON_ONCE(ext4_test_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA))) + return -EINVAL; /* * Since the inode is new it is ok to pass the * XATTR_CREATE flag. This is necessary to match the @@ -170,21 +178,10 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, * function with the credits allocated for the new * inode. */ - res = ext4_xattr_set_handle(handle, inode, - EXT4_XATTR_INDEX_ENCRYPTION, - EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, - ctx, len, XATTR_CREATE); - if (!res) { - ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT); - ext4_clear_inode_state(inode, - EXT4_STATE_MAY_INLINE_DATA); - /* - * Update inode->i_flags - S_ENCRYPTED will be enabled, - * S_DAX may be disabled - */ - ext4_set_inode_flags(inode, false); - } - return res; + return ext4_xattr_set_handle(handle, inode, + EXT4_XATTR_INDEX_ENCRYPTION, + EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, + ctx, len, XATTR_CREATE); } res = dquot_initialize(inode); diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index a40cb27f8116..3848244af77a 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -997,6 +997,8 @@ struct inode *__ext4_new_inode(struct mnt_idmap *idmap, err = fscrypt_prepare_new_inode(dir, inode, &encrypt); if (err) goto out; + if (encrypt) + i_flags |= EXT4_ENCRYPT_FL; } err = dquot_initialize(inode); @@ -1306,6 +1308,7 @@ struct inode *__ext4_new_inode(struct mnt_idmap *idmap, ei->i_extra_isize = sbi->s_want_extra_isize; ei->i_inline_off = 0; if (ext4_has_feature_inline_data(sb) && + !(ei->i_flags & EXT4_ENCRYPT_FL) && (!(ei->i_flags & (EXT4_DAX_FL|EXT4_EA_INODE_FL)) || S_ISDIR(mode))) ext4_set_inode_state(inode, EXT4_STATE_MAY_INLINE_DATA); ret = inode;