Re: [PATCH -V1 05/22] vfs: Add new file and directory create permission flags

Jeff Layton
2014-04-28T11:23:10Z

On Sun, 27 Apr 2014 21:44:36 +0530
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

> From: Andreas Gruenbacher <agruen@kernel.org>
>
> Some permission models distinguish between the permission to create a
> non-directory and a directory. Pass this information down to
> inode_permission() as mask flags
>
> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
> fs/namei.c | 21 ++++++++++++---------
> include/linux/fs.h | 2 ++
> 2 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/fs/namei.c b/fs/namei.c
> index 7d93d195f0e5..028bc8bcf77c 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -445,7 +445,8 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
> * this, letting us set arbitrary permissions for filesystem access without
> * changing the "normal" UIDs which are used for other things.
> *
> - * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
> + * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR,
> + * MAY_WRITE must also be set in @mask.
> */
> int inode_permission(struct inode *inode, int mask)
> {
> @@ -2444,14 +2445,16 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
> * 3. We should have write and exec permissions on dir
> * 4. We can't do it if dir is immutable (done in permission())
> */
> -static inline int may_create(struct inode *dir, struct dentry *child)
> +static inline int may_create(struct inode *dir, struct dentry *child, bool isdir)
> {
> + int mask = isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE;
> +
> audit_inode_child(dir, child, AUDIT_TYPE_CHILD_CREATE);
> if (child->d_inode)
> return -EEXIST;
> if (IS_DEADDIR(dir))
> return -ENOENT;
> - return inode_permission(dir, MAY_WRITE | MAY_EXEC);
> + return inode_permission(dir, MAY_WRITE | MAY_EXEC | mask);
> }
>
> /*
> @@ -2501,7 +2504,7 @@ EXPORT_SYMBOL(unlock_rename);
> int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
> bool want_excl)
> {
> - int error = may_create(dir, dentry);
> + int error = may_create(dir, dentry, 0);

nit: since the third argument here is a bool, this should be "false"
and not "0". Ditto for all of the other calls of may_create.

> if (error)
> return error;
>
> @@ -3363,7 +3366,7 @@ EXPORT_SYMBOL(user_path_create);
>
> int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
> {
> - int error = may_create(dir, dentry);
> + int error = may_create(dir, dentry, 0);
>
> if (error)
> return error;
> @@ -3455,7 +3458,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, d
>
> int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
> {
> - int error = may_create(dir, dentry);
> + int error = may_create(dir, dentry, 1);
> unsigned max_links = dir->i_sb->s_max_links;
>
> if (error)
> @@ -3785,7 +3788,7 @@ SYSCALL_DEFINE1(unlink, const char __user *, pathname)
>
> int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
> {
> - int error = may_create(dir, dentry);
> + int error = may_create(dir, dentry, 0);
>
> if (error)
> return error;
> @@ -3871,7 +3874,7 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
> if (S_ISDIR(inode->i_mode))
> return -EPERM;
>
> - error = may_create(dir, new_dentry);
> + error = may_create(dir, new_dentry, 0);
> if (error)
> return error;
>
> @@ -4062,7 +4065,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
> return error;
>
> if (!target) {
> - error = may_create(new_dir, new_dentry);
> + error = may_create(new_dir, new_dentry, is_dir);
> } else {
> new_is_dir = d_is_dir(new_dentry);
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 1f524b4b652d..da5521de04ab 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -77,6 +77,8 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
> #define MAY_CHDIR 0x00000040
> /* called from RCU mode, don't block */
> #define MAY_NOT_BLOCK 0x00000080
> +#define MAY_CREATE_FILE 0x00000100
> +#define MAY_CREATE_DIR 0x00000200
>
> /*
> * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond

--
Jeff Layton <jlayton@poochiereds.net>