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    SubjectRe: [PATCH -V4 08/11] vfs: Add new file and directory create permission flags
    On Fri, 24 Sep 2010 18:18:11 +0530
    "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:

    > From: Andreas Gruenbacher <agruen@suse.de>
    >
    > 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@suse.de>
    > 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 b0b8a71..ed786b2 100644
    > --- a/fs/namei.c
    > +++ b/fs/namei.c
    > @@ -253,7 +253,8 @@ int generic_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)
    > {
    > @@ -1337,13 +1338,15 @@ 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)
    ^^^^^
    nit: maybe saner as a bool?
    > {
    > + 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);
    > }
    >
    > /*
    > @@ -1391,7 +1394,7 @@ 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;
    > @@ -1953,7 +1956,7 @@ EXPORT_SYMBOL_GPL(lookup_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;
    > @@ -2057,7 +2060,7 @@ 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;
    > @@ -2342,7 +2345,7 @@ 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;
    > @@ -2415,7 +2418,7 @@ int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_de
    > if (!inode)
    > return -ENOENT;
    >
    > - error = may_create(dir, new_dentry);
    > + error = may_create(dir, new_dentry, S_ISDIR(inode->i_mode));

    ^^^^ this is a little
    scary, but even if it's
    a directory, it'll get
    kicked out in a later
    check. Would it be
    clearer to move up the
    S_ISDIR() check in this
    function and then pass
    this in as false?

    > if (error)
    > return error;
    >
    > @@ -2631,7 +2634,7 @@ 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 26fc8ae..5dc1ebd 100644
    > --- a/include/linux/fs.h
    > +++ b/include/linux/fs.h
    > @@ -55,6 +55,8 @@ struct inodes_stat_t {
    > #define MAY_ACCESS 16
    > #define MAY_OPEN 32
    > #define MAY_CHDIR 64
    > +#define MAY_CREATE_FILE 128
    > +#define MAY_CREATE_DIR 256
    >
    > /*
    > * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond


    --
    Jeff Layton <jlayton@redhat.com>


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