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    Subject[PATCH -V7 09/26] vfs: Add delete child and delete self permission flags
    Date
    From: Andreas Gruenbacher <agruen@kernel.org>

    Normally, deleting a file requires write access to the parent directory.
    Some permission models use a different permission on the parent
    directory to indicate delete access. In addition, a process can have
    per-file delete access even without delete access on the parent
    directory.

    Introduce two new inode_permission() mask flags and use them in
    may_delete()

    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 | 42 ++++++++++++++++++++++++++++--------------
    include/linux/fs.h | 2 ++
    2 files changed, 30 insertions(+), 14 deletions(-)

    diff --git a/fs/namei.c b/fs/namei.c
    index f6184b8..7bf42e8 100644
    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -337,7 +337,7 @@ static inline int do_inode_permission(struct inode *inode, int mask)
    * are used for other things.
    *
    * When checking for MAY_APPEND, MAY_CREATE_FILE, MAY_CREATE_DIR,
    - * MAY_WRITE must also be set in @mask.
    + * MAY_DELETE_CHILD, MAY_DELETE_SELF, MAY_WRITE must also be set in @mask.
    */
    int inode_permission(struct inode *inode, int mask)
    {
    @@ -1853,7 +1853,7 @@ static inline int check_sticky(struct inode *dir, struct inode *inode)
    return 0;

    other_userns:
    - return !ns_capable(inode_userns(inode), CAP_FOWNER);
    + return 1;
    }

    /*
    @@ -1875,30 +1875,44 @@ other_userns:
    * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
    * nfs_async_unlink().
    */
    -static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
    +static int may_delete(struct inode *dir, struct dentry *victim,
    + int isdir, int replace)
    {
    - int error;
    + struct inode *inode = victim->d_inode;
    + int mask, replace_mask = 0, error, is_sticky;
    +

    - if (!victim->d_inode)
    + if (!inode)
    return -ENOENT;

    BUG_ON(victim->d_parent->d_inode != dir);
    audit_inode_child(victim, dir);

    - error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
    + mask = MAY_WRITE | MAY_EXEC | MAY_DELETE_CHILD;
    + if (replace)
    + replace_mask = S_ISDIR(inode->i_mode) ?
    + MAY_CREATE_DIR : MAY_CREATE_FILE;
    + is_sticky = check_sticky(dir, inode);
    + error = inode_permission(dir, mask | replace_mask);
    + if ((error || is_sticky) && IS_RICHACL(inode) &&
    + (inode_permission(dir, MAY_EXEC | replace_mask) == 0) &&
    + (inode_permission(inode, MAY_DELETE_SELF) == 0))
    + error = 0;
    + else if (!error && is_sticky &&
    + !ns_capable(inode_userns(inode), CAP_FOWNER))
    + error = -EPERM;
    if (error)
    return error;
    if (IS_APPEND(dir))
    return -EPERM;
    - if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
    - IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
    + if (IS_APPEND(inode) || IS_IMMUTABLE(inode) || IS_SWAPFILE(inode))
    return -EPERM;
    if (isdir) {
    - if (!S_ISDIR(victim->d_inode->i_mode))
    + if (!S_ISDIR(inode->i_mode))
    return -ENOTDIR;
    if (IS_ROOT(victim))
    return -EBUSY;
    - } else if (S_ISDIR(victim->d_inode->i_mode))
    + } else if (S_ISDIR(inode->i_mode))
    return -EISDIR;
    if (IS_DEADDIR(dir))
    return -ENOENT;
    @@ -2605,7 +2619,7 @@ void dentry_unhash(struct dentry *dentry)

    int vfs_rmdir(struct inode *dir, struct dentry *dentry)
    {
    - int error = may_delete(dir, dentry, 1);
    + int error = may_delete(dir, dentry, 1, 0);

    if (error)
    return error;
    @@ -2700,7 +2714,7 @@ SYSCALL_DEFINE1(rmdir, const char __user *, pathname)

    int vfs_unlink(struct inode *dir, struct dentry *dentry)
    {
    - int error = may_delete(dir, dentry, 0);
    + int error = may_delete(dir, dentry, 0, 0);

    if (error)
    return error;
    @@ -3096,14 +3110,14 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
    if (old_dentry->d_inode == new_dentry->d_inode)
    return 0;

    - error = may_delete(old_dir, old_dentry, is_dir);
    + error = may_delete(old_dir, old_dentry, is_dir, 0);
    if (error)
    return error;

    if (!new_dentry->d_inode)
    error = may_create(new_dir, new_dentry, is_dir);
    else
    - error = may_delete(new_dir, new_dentry, is_dir);
    + error = may_delete(new_dir, new_dentry, is_dir, 1);
    if (error)
    return error;

    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index 60361c6..ccece40 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -69,6 +69,8 @@ struct inodes_stat_t {
    #define MAY_NOT_BLOCK 0x00000080
    #define MAY_CREATE_FILE 0x00000100
    #define MAY_CREATE_DIR 0x00000200
    +#define MAY_DELETE_CHILD 0x00000400
    +#define MAY_DELETE_SELF 0x00000800

    /*
    * flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond
    --
    1.7.5.4


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