ntfs: respect per-file chmod mode over mount masks

fmask and dmask provide the default permissions for files without WSL
metadata. Once chmod stores a mode in $LXMOD, however, that per-file mode
must take precedence so selected files can retain permissions such as
execute across remounts.

Record whether $LXMOD was found while loading an inode and apply the mount
masks only when it is absent. Do not remask the in-memory mode after
setattr persists it. Continue loading $LXMOD even when optional $LXUID or
$LXGID metadata is missing, since chmod may create only $LXMOD.

Fixes: fc053f05ca28 ("ntfs: add reparse and ea operations")
Reviewed-by: Hyunchul Lee <hyc.lee@gmail.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>

5 files changed, 24 insertions, 28 deletions

diff --git a/fs/ntfs/ea.c b/fs/ntfs/ea.c
index 4fb10d51211c..4fbea76afe7e 100644
--- a/fs/ntfs/ea.c
+++ b/fs/ntfs/ea.c
@@ -406,37 +406,35 @@ out:
  * Check for the presence of an EA "$LXDEV" (used by WSL)
  * and return its value as a device address
  */
-int ntfs_ea_get_wsl_inode(struct inode *inode, dev_t *rdevp, unsigned int flags)
+int ntfs_ea_get_wsl_inode(struct inode *inode, dev_t *rdevp, unsigned int flags,
+			  bool *has_lxmod)
 {
 	int err;
 	__le32 v;
 
+	*has_lxmod = false;
+
 	if (!(flags & NTFS_VOL_UID)) {
 		/* Load uid to lxuid EA */
 		err = ntfs_get_ea(inode, "$LXUID", sizeof("$LXUID") - 1, &v,
 				sizeof(v));
-		if (err < 0)
-			return err;
-		if (err != sizeof(v))
-			return -EIO;
-		i_uid_write(inode, le32_to_cpu(v));
+		if (err == sizeof(v))
+			i_uid_write(inode, le32_to_cpu(v));
 	}
 
 	if (!(flags & NTFS_VOL_GID)) {
 		/* Load gid to lxgid EA */
 		err = ntfs_get_ea(inode, "$LXGID", sizeof("$LXGID") - 1, &v,
 				sizeof(v));
-		if (err < 0)
-			return err;
-		if (err != sizeof(v))
-			return -EIO;
-		i_gid_write(inode, le32_to_cpu(v));
+		if (err == sizeof(v))
+			i_gid_write(inode, le32_to_cpu(v));
 	}
 
 	/* Load mode to lxmod EA */
 	err = ntfs_get_ea(inode, "$LXMOD", sizeof("$LXMOD") - 1, &v, sizeof(v));
 	if (err == sizeof(v)) {
 		inode->i_mode = le32_to_cpu(v);
+		*has_lxmod = true;
 	} else {
 		/* Everyone gets all permissions. */
 		inode->i_mode |= 0777;
diff --git a/fs/ntfs/ea.h b/fs/ntfs/ea.h
index 1f63bd55e057..acb39c2a6fbc 100644
--- a/fs/ntfs/ea.h
+++ b/fs/ntfs/ea.h
@@ -10,7 +10,8 @@
 extern const struct xattr_handler *const ntfs_xattr_handlers[];
 
 int ntfs_ea_set_wsl_not_symlink(struct ntfs_inode *ni, mode_t mode, dev_t dev);
-int ntfs_ea_get_wsl_inode(struct inode *inode, dev_t *rdevp, unsigned int flags);
+int ntfs_ea_get_wsl_inode(struct inode *inode, dev_t *rdevp, unsigned int flags,
+			  bool *has_lxmod);
 int ntfs_ea_set_wsl_inode(struct inode *inode, dev_t rdev, __le16 *ea_size,
 		unsigned int flags);
 ssize_t ntfs_listxattr(struct dentry *dentry, char *buffer, size_t size);
diff --git a/fs/ntfs/file.c b/fs/ntfs/file.c
index c8e49f83fd92..d4282822b3ce 100644
--- a/fs/ntfs/file.c
+++ b/fs/ntfs/file.c
@@ -342,14 +342,12 @@ int ntfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 		if (ia_valid & ATTR_MODE)
 			flags |= NTFS_EA_MODE;
 
-		if (S_ISDIR(vi->i_mode))
-			vi->i_mode &= ~vol->dmask;
-		else
-			vi->i_mode &= ~vol->fmask;
-
 		mutex_lock(&ni->mrec_lock);
-		ntfs_ea_set_wsl_inode(vi, 0, NULL, flags);
+		err = ntfs_ea_set_wsl_inode(vi, 0, NULL, flags);
 		mutex_unlock(&ni->mrec_lock);
+		if (err)
+			goto out;
+
 	}
 
 	mark_inode_dirty(vi);
diff --git a/fs/ntfs/inode.c b/fs/ntfs/inode.c
index 50e244aa372e..39c7fd8c1149 100644
--- a/fs/ntfs/inode.c
+++ b/fs/ntfs/inode.c
@@ -682,6 +682,7 @@ static int ntfs_read_locked_inode(struct inode *vi)
 	unsigned int name_len = 4, flags = 0;
 	int extend_sys = 0;
 	dev_t dev = 0;
+	bool has_lxmod = false;
 	bool vol_err = true;
 
 	ntfs_debug("Entering for i_ino 0x%llx.", ni->mft_no);
@@ -862,7 +863,7 @@ skip_attr_list_load:
 	err = ntfs_attr_lookup(AT_EA_INFORMATION, NULL, 0, 0, 0, NULL, 0, ctx);
 	if (!err) {
 		NInoSetHasEA(ni);
-		ntfs_ea_get_wsl_inode(vi, &dev, flags);
+		ntfs_ea_get_wsl_inode(vi, &dev, flags, &has_lxmod);
 	}
 
 	if (ni->flags & FILE_ATTR_REPARSE_POINT) {
@@ -886,16 +887,18 @@ skip_attr_list_load:
 
 	if (S_ISDIR(vi->i_mode)) {
 		/*
-		 * Apply the directory permissions mask set in the mount
-		 * options.
+		 * Apply the directory permissions mask set in the mount options
+		 * when no per-file WSL mode is present.
 		 */
-		vi->i_mode &= ~vol->dmask;
+		if (!has_lxmod)
+			vi->i_mode &= ~vol->dmask;
 		/* Things break without this kludge! */
 		if (vi->i_nlink > 1)
 			set_nlink(vi, 1);
 	} else {
-		/* Apply the file permissions mask set in the mount options. */
-		vi->i_mode &= ~vol->fmask;
+		/* Apply the file permissions mask when no WSL mode is present. */
+		if (!has_lxmod)
+			vi->i_mode &= ~vol->fmask;
 	}
 
 	/*
diff --git a/fs/ntfs/namei.c b/fs/ntfs/namei.c
index 0de5b63ef407..7091b2496fac 100644
--- a/fs/ntfs/namei.c
+++ b/fs/ntfs/namei.c
@@ -424,8 +424,6 @@ static struct ntfs_inode *__ntfs_create(struct mnt_idmap *idmap, struct inode *d
 	 * directories, also setup the index values to the defaults.
 	 */
 	if (S_ISDIR(mode)) {
-		mode &= ~vol->dmask;
-
 		NInoSetMstProtected(ni);
 		ni->itype.index.block_size = 4096;
 		ni->itype.index.block_size_bits = ntfs_ffs(4096) - 1;
@@ -439,8 +437,6 @@ static struct ntfs_inode *__ntfs_create(struct mnt_idmap *idmap, struct inode *d
 			ni->itype.index.vcn_size_bits =
 				vol->sector_size_bits;
 		}
-	} else {
-		mode &= ~vol->fmask;
 	}
 
 	if (IS_RDONLY(vi))