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ext4: don't enable DAX on new encrypted files

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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 043546e46d ("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 <disgoel@linux.ibm.com>
Reported-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Closes: https://lore.kernel.org/r/20260723085648.1500357-1-ojaswin@linux.ibm.com
Fixes: 043546e46d ("fs/ext4: Only change S_DAX on inode load")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Tested-by: Disha Goel <disgoel@linux.ibm.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260730175212.36923-1-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers
2026-07-30 10:52:12 -07:00
committed by Theodore Ts'o
parent f7237a775c
commit da32af420d
2 changed files with 24 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
fs/ext4/crypto.c
View File

@@ -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)

4
fs/ext4/ialloc.c
View File

@@ -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;