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

Aneesh Kumar K.V
2014-04-27T16:16:42Z

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);
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
--
1.9.1