Re: [PATCH -V1 06/22] vfs: Add delete child and delete self permission flags

Aneesh Kumar K.V
2014-05-01T15:18:19Z

Dave Chinner <david@fromorbit.com> writes:

> On Sun, Apr 27, 2014 at 09:44:37PM +0530, Aneesh Kumar K.V wrote:
>> 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()
>>
>> Signed-off-by: Andreas Gruenbacher <agruen@kernel.org>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>> ---
>> fs/namei.c | 45 ++++++++++++++++++++++++++++++++++-----------
>> include/linux/fs.h | 2 ++
>> 2 files changed, 36 insertions(+), 11 deletions(-)
>>
>> diff --git a/fs/namei.c b/fs/namei.c
>> index 028bc8bcf77c..56ac7613fbca 100644
>> --- a/fs/namei.c
>> +++ b/fs/namei.c
>> @@ -446,7 +446,7 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
>> * changing the "normal" UIDs which 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)
>> {
>> @@ -2366,11 +2366,25 @@ kern_path_mountpoint(int dfd, const char *name, struct path *path,
>> }
>> EXPORT_SYMBOL(kern_path_mountpoint);
>>
>> +
>> +/*
>> + * We should have exec permission on directory and MAY_DELETE_SELF
>> + * on the object being deleted.
>> + */
>> +static int richacl_may_selfdelete(struct inode *dir,
>> + struct inode *inode, int replace_mask)
>> +{
>> + return (IS_RICHACL(inode) &&
>> + (inode_permission(dir, MAY_EXEC | replace_mask) == 0) &&
>> + (inode_permission(inode, MAY_DELETE_SELF) == 0));
>> +}
>
> Can't say I like these "richacl" prefixes. Why not just "may_*"
> like all the other permission checks?

Will update.

>
>
>> @@ -2414,13 +2431,19 @@ static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
>> BUG_ON(victim->d_parent->d_inode != dir);
>> audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
>>
>> - 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;
>> + error = inode_permission(dir, mask | replace_mask);
>> + if (error && richacl_may_selfdelete(dir, inode, replace_mask))
>> + error = 0;

....

>>
>> if (!(flags & RENAME_EXCHANGE))
>> - error = may_delete(new_dir, new_dentry, is_dir);
>> + error = may_delete(new_dir, new_dentry, is_dir, 1);
>> else
>> - error = may_delete(new_dir, new_dentry, new_is_dir);
>> + error = may_delete(new_dir, new_dentry, new_is_dir, 1);
>
> Another boolean parameter that means nothing at the call site. This
> should really be passing a flags field, not a bunch of booleans that
> are simply evaluated into flags...
>

Will update

Thanks
-aneesh