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Thu, 30 Jul 2026 08:35:28 +0000 (GMT) Received: from [9.123.9.194] (unknown [9.123.9.194]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 30 Jul 2026 08:35:28 +0000 (GMT) Message-ID: <3686bf0f-1fd9-4699-a1b2-88dce3787906@linux.ibm.com> Date: Thu, 30 Jul 2026 14:05:27 +0530 Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ext4: turn off DAX on new files when encryption is set To: Eric Biggers , Jan Kara , Ojaswin Mujoo Cc: linux-ext4@vger.kernel.org, "Theodore Ts'o" , Ritesh Harjani , Zhang Yi , linux-kernel@vger.kernel.org, Baokun Li References: <20260723085648.1500357-1-ojaswin@linux.ibm.com> <20260727194350.GC1021387@google.com> <20260727201339.GD1021387@google.com> Content-Language: en-GB From: Disha Goel In-Reply-To: <20260727201339.GD1021387@google.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-GUID: wRYWAYBPhFbO0EvPrKwRHEr29diLIuBy X-Proofpoint-ORIG-GUID: yqtKqoX1zlzuFE8119x1bZK3D8Mr01P7 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMwMDA1OSBTYWx0ZWRfX9y5WM8KJQLbX 5rse5H8hgk1vwatJEEpSeUsDrYmYxoUkNArKI5MvhPjrNxhRjEKiIMDrnOLUp5nE99gIXEjmvYq T3RLCkTorLLlEpWEi24UGiWfPCIQ2NMziaL9iY+O/lWJ4iIfPwfgIhjM331ahmEPBZrI8OSwPE/ Ra8MDE1tQUYi7LVkqGbsBORmxTjwFxT7A0Ue6N2aqk7A8+pbUeNzMUD8ed/VaCBjf/JTaTXl49L YzE4e+AogHg0QoTDbruFgBLmWI6YJp+78cvuflqjTPdekg/Vcpe3rmIEECEJA8DSCvFCfu6s2Mr 9DzdGxrzlxMLGknhydKAKPHtz7Hz30p/Ar+5kftgWfns43iKsJfc8F+aFxjKyCVqncig/CRMStG Eldwjj3OzUbovvdR6aG9g+J7IGW45ckjvBxax6/1SbAeQnn/rwMFfX6Ydlz8UhzPSSXd8wIFPoQ ceBnF6Jdton5/if1Pbg== X-Authority-Analysis: v=2.4 cv=SKFykuvH c=1 sm=1 tr=0 ts=6a6b0cd5 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=JKVybEi45UZxgy7gOqIA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMwMDA1OSBTYWx0ZWRfXw97hYlArJ92p NtBPXlYc5yKD1j2Ef2/CiMP9AAZECDS0loLnCauXWN4ZuOJJUIJUgDjrRner1GmAZBYmnW1Qx65 1UxsEPnBqV9hKg6NYq84zM6XYaUBy9E= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-30_02,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607300059 On 28/07/26 1:43 am, Eric Biggers wrote: > 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(). Hi Eric, I have tested it in my setup. All failing encryption tests in the generic group passed. > > 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; -- Regards, Disha