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vfs: pass S_IFDIR mode to vfs_prepare_mode()

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There is a comment in vfs_prepare_mode() that says:

  Note that it's currently valid for @type to be 0 if a directory is
  created. Filesystems raise that flag individually and we need to check
  whether each filesystem can deal with receiving S_IFDIR from the vfs
  before we enforce a non-zero type.

It is safe to do this clean-up except that three filesystems (fuse,
cifs, and coda) forward the mkdir @mode unchanged to something outside
the kernel. Mask S_IFDIR back out in coda_mkdir(), fuse_mkdir() and
cifs_mkdir() so that what is sent outside the kernel is unchanged.
Their maintainers can drop the mask once they have confirmed it is safe.

Assisted-by: LLM
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20260630105400.68459-2-jkoolstra@xs4all.nl
Reviewed-by: NeilBrown <neil@brown.name>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Jori Koolstra 2026-06-30 12:53:30 +02:00 committed by Christian Brauner
parent af695109e8
commit 2f3a7a488c
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
4 changed files with 22 additions and 7 deletions
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7
fs/coda/dir.c
View File

@ -179,7 +179,12 @@ static struct dentry *coda_mkdir(struct mnt_idmap *idmap, struct inode *dir,
if (is_root_inode(dir) && coda_iscontrol(name, len))
return ERR_PTR(-EPERM);
attrs.va_mode = mode;
/*
* vfs_mkdir() now passes S_IFDIR in @mode, but @mode is forwarded
* verbatim to userspace, which has only ever been given the permission
* bits. Strip the type bit until venus is known to cope with it.
*/
attrs.va_mode = mode & ~S_IFDIR;
error = venus_mkdir(dir->i_sb, coda_i2f(dir),
name, len, &newfid, &attrs);
if (error)

8
fs/fuse/dir.c
View File

@ -1117,6 +1117,14 @@ static struct dentry *fuse_mkdir(struct mnt_idmap *idmap, struct inode *dir,
if (!fm->fc->dont_mask)
mode &= ~current_umask();
/*
* vfs_mkdir() now passes S_IFDIR in @mode, but @mode is forwarded
* verbatim to the userspace server which has only ever been given the
* permission bits. Strip the type bit until the protocol is known to
* cope with it.
*/
mode &= ~S_IFDIR;
memset(&inarg, 0, sizeof(inarg));
inarg.mode = mode;
inarg.umask = current_umask();

7
fs/namei.c
View File

@ -4140,11 +4140,6 @@ EXPORT_SYMBOL(end_renaming);
* after setgid stripping allows the same ordering for both non-POSIX ACL and
* POSIX ACL supporting filesystems.
*
* Note that it's currently valid for @type to be 0 if a directory is created.
* Filesystems raise that flag individually and we need to check whether each
* filesystem can deal with receiving S_IFDIR from the vfs before we enforce a
* non-zero type.
*
* Returns: mode to be passed to the filesystem
*/
static inline umode_t vfs_prepare_mode(struct mnt_idmap *idmap,
@ -5256,7 +5251,7 @@ struct dentry *vfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
if (!dir->i_op->mkdir)
goto err;
mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, 0);
mode = vfs_prepare_mode(idmap, dir, mode, S_IRWXUGO | S_ISVTX, S_IFDIR);
error = security_inode_mkdir(dir, dentry, mode);
if (error)
goto err;

7
fs/smb/client/inode.c
View File

@ -2282,6 +2282,13 @@ struct dentry *cifs_mkdir(struct mnt_idmap *idmap, struct inode *inode,
const char *full_path;
void *page;
/*
* vfs_mkdir() now passes S_IFDIR in @mode, but @mode is forwarded
* verbatim to the server and in the past only contained permission
* bits. Strip the type bit until SMB is verified to deal with it.
*/
mode &= ~S_IFDIR;
cifs_dbg(FYI, "In cifs_mkdir, mode = %04ho inode = 0x%p\n",
mode, inode);