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Subject[PATCH -V7 08/26] vfs: Add new file and directory create permission flags
Date
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

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/namei.c | 26 +++++++++++++++-----------
include/linux/fs.h | 2 ++
2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index cf8b2f0..f6184b8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -336,7 +336,8 @@ static inline int do_inode_permission(struct inode *inode, int mask)
* 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)
{
@@ -1914,13 +1915,15 @@ static int may_delete(struct inode *dir,struct dentry *victim,int 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, int isdir)
{
+ int mask = isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE;
+
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);
}

/*
@@ -1968,7 +1971,7 @@ void unlock_rename(struct dentry *p1, struct dentry *p2)
int vfs_create(struct inode *dir, struct dentry *dentry, int mode,
struct nameidata *nd)
{
- int error = may_create(dir, dentry);
+ int error = may_create(dir, dentry, 0);

if (error)
return error;
@@ -2427,7 +2430,7 @@ EXPORT_SYMBOL(user_path_create);

int vfs_mknod(struct inode *dir, struct dentry *dentry, int mode, dev_t dev)
{
- int error = may_create(dir, dentry);
+ int error = may_create(dir, dentry, 0);

if (error)
return error;
@@ -2524,7 +2527,7 @@ SYSCALL_DEFINE3(mknod, const char __user *, filename, int, mode, unsigned, dev)

int vfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
- int error = may_create(dir, dentry);
+ int error = may_create(dir, dentry, 1);

if (error)
return error;
@@ -2806,7 +2809,7 @@ 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;
@@ -2872,7 +2875,10 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
if (!inode)
return -ENOENT;

- error = may_create(dir, new_dentry);
+ if (S_ISDIR(inode->i_mode))
+ return -EPERM;
+
+ error = may_create(dir, new_dentry, 0);
if (error)
return error;

@@ -2886,8 +2892,6 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
return -EPERM;
if (!dir->i_op->link)
return -EPERM;
- if (S_ISDIR(inode->i_mode))
- return -EPERM;

error = security_inode_link(old_dentry, dir, new_dentry);
if (error)
@@ -3097,7 +3101,7 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
return error;

if (!new_dentry->d_inode)
- error = may_create(new_dir, new_dentry);
+ error = may_create(new_dir, new_dentry, is_dir);
else
error = may_delete(new_dir, new_dentry, is_dir);
if (error)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index f3ebf86..60361c6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -67,6 +67,8 @@ struct inodes_stat_t {
#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
--
1.7.5.4


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