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



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