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Mon, 3 Aug 2026 08:00:50 +0000 (GMT) Message-ID: <17e787ea-7e0b-4887-b736-4e2f3dbeb245@linux.ibm.com> Date: Mon, 3 Aug 2026 13:30:48 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] ext4: don't enable DAX on new encrypted files Content-Language: en-GB To: Eric Biggers , linux-ext4@vger.kernel.org, "Theodore Ts'o" Cc: Andreas Dilger , Baokun Li , Jan Kara , Ojaswin Mujoo , Ritesh Harjani , Zhang Yi , Ira Weiny , linux-fscrypt@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20260730175212.36923-1-ebiggers@kernel.org> From: Disha Goel In-Reply-To: <20260730175212.36923-1-ebiggers@kernel.org> 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-Authority-Analysis: v=2.4 cv=E6P9Y6dl c=1 sm=1 tr=0 ts=6a704aba cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=ovQU41l7dhj9IMd-MlgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: b79nUqRkScouH3xfu6JhLmjGCmnklbvZ X-Proofpoint-GUID: 2z1O-lX0C4CUH2UlfhrSL0VakxhqMogu X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDA2OCBTYWx0ZWRfXw8ABikuV8BfK XcS1/+zYfb6uAovv5Gnb1404YgLMKDzde8Z32ZevKrf1U62vCAyYqtGRfRZgpxsoyP2XsCUm6cp u/fIMno0CQFf/iACaphhSCfd6eMYBa4= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDA2OCBTYWx0ZWRfX/F1Yo/aj7dgw i0p6jkjgIMCtPlgxwtqcTrOZODsGZT3rS4LQ15Wk94jN/k84vL9B5vL7i1EYqcbiR4+PuD8TFhB wKJYkDkCC3sVi5OK0nNqINSJt3a8OsXI8Kagjo7KMbEJ6SXACYNRUPaH88tESWbLOQqnL6u6eCo cYIdE4ZhZnlJaduJo/Ao6XrqSDVgwQXpkTCQnh3fGFeHK5wK/H2B0xedA3h6q2HW2QvBjoSSm32 1EDoGR9Nmju+BI56FGlS44UV35x5+w0ipFtDXqs+Ymh8s0kv2b1la9nkKElCOEquJMHARh3LMTl zEM+6oKKK1cEHF6Lq0nIDF5XabLMUW4mJLjucb9eOJSAMpaqgxFtPL+lJYqNnlP9o1uiO69rU+3 zw+uYuAdSNBLcg4PkIwlpvxn3GIcb2dVxel0KUGS6pSH1nORxxrwHfMisoCLgiKxA1MARE6/r72 Xwl2RN83Q4yzhNwf7eA== 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=2026-08-02_06,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 clxscore=1011 lowpriorityscore=0 priorityscore=1501 suspectscore=0 adultscore=0 spamscore=0 malwarescore=0 impostorscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608030068 On 30/07/26 11:22 pm, Eric Biggers wrote: > Currently, when a new encrypted regular file is created, the call to > ext4_set_inode_flags(inode, init=true) in __ext4_new_inode() is made > before EXT4_INODE_ENCRYPT is set. As a result, it can set S_DAX if the > filesystem is mounted with "-o dax=always". > > EXT4_INODE_ENCRYPT then actually gets set a bit later in > __ext4_new_inode(), when it calls fscrypt_set_context() which calls > ext4_set_context(). ext4_set_context() sets EXT4_INODE_ENCRYPT and > calls ext4_set_inode_flags(inode, init=false) to set S_ENCRYPTED too. > > This was intended to clear S_DAX as well. However, this was broken by > commit 043546e46dc7 ("fs/ext4: Only change S_DAX on inode load"). This > causes data written to the file to bypass encryption, also causing > xfstests failures such as generic/548 (when "-o dax=always" is used). > > Fix this by simplifying the flow by making __ext4_new_inode() set > EXT4_INODE_ENCRYPT earlier. This makes it take effect in > ext4_set_inode_flags(inode, init=true), making S_DAX never be set. > > Similarly, make EXT4_STATE_MAY_INLINE_DATA never be set in the first > place on new encrypted inodes. Then it doesn't need to be cleared. > > As a result of these simplifications, ext4_set_context() no longer needs > to change inode flags or state when 'handle != NULL'. Remove that too. > > Reported-by: Disha Goel > Reported-by: Ojaswin Mujoo > Closes: https://lore.kernel.org/r/20260723085648.1500357-1-ojaswin@linux.ibm.com > Fixes: 043546e46dc7 ("fs/ext4: Only change S_DAX on inode load") > Cc: stable@vger.kernel.org > Signed-off-by: Eric Biggers I have tested on a -o dax=always ext4 filesystem on ppc64le with the following xfstests configuration. All failing encryption tests in the generic group now pass. MOUNT_OPTIONS="-o block_validity,dax" MKFS_OPTIONS="-b 65536" Feel free to add Tested-by: Disha Goel > --- > fs/ext4/crypto.c | 40 ++++++++++++++++++++-------------------- > fs/ext4/ialloc.c | 4 ++++ > 2 files changed, 24 insertions(+), 20 deletions(-) > > diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c > index f41f320f4437..3971986de028 100644 > --- a/fs/ext4/crypto.c > +++ b/fs/ext4/crypto.c > @@ -144,7 +144,13 @@ 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))) > + /* > + * For new encrypted inodes, S_DAX is never set in the first place. > + * > + * For existing inodes, this is called only on empty directories. ext4 > + * never sets S_DAX on directories. > + */ > + if (WARN_ON_ONCE(IS_DAX(inode))) > return -EINVAL; > > if (ext4_test_inode_flag(inode, EXT4_INODE_DAX)) > @@ -163,6 +169,14 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, > */ > > if (handle) { > + /* > + * __ext4_new_inode() should have already set the encrypt flag > + * on the inode and avoided enabling 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 +184,10 @@ 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); > @@ -205,10 +208,7 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len, > ctx, len, 0); > if (!res) { > ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT); > - /* > - * Update inode->i_flags - S_ENCRYPTED will be enabled, > - * S_DAX may be disabled > - */ > + /* Update inode->i_flags to set S_ENCRYPTED. */ > ext4_set_inode_flags(inode, false); > res = ext4_mark_inode_dirty(handle, inode); > if (res) > diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c > index a40cb27f8116..a5831fc536db 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 +1308,8 @@ 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) && > + /* Encrypted inodes cannot have inline data */ > + !(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; > > base-commit: f5098b6bae761e346ebcd9da7f95622c04733cff -- Regards, Disha