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Subject[PATCH v25 03/22] vfs: Add MAY_DELETE_SELF and MAY_DELETE_CHILD permission flags
Date
Normally, deleting a file requires MAY_WRITE access to the parent
directory. With richacls, a file may be deleted with MAY_DELETE_CHILD access
to the parent directory or with MAY_DELETE_SELF access to the file.

To support that, pass the MAY_DELETE_CHILD mask flag to inode_permission()
when checking for delete access inside a directory, and MAY_DELETE_SELF
when checking for delete access to a file itself.

The MAY_DELETE_SELF permission overrides the sticky directory check.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Reviewed-by: Steve French <steve.french@primarydata.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
---
fs/namei.c | 20 +++++++++++++-------
include/linux/fs.h | 2 ++
2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/fs/namei.c b/fs/namei.c
index 6cd7a10..4292c33 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -463,9 +463,9 @@ static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
* this, letting us set arbitrary permissions for filesystem access without
* changing the "normal" UIDs which are used for other things.
*
- * MAY_WRITE must be set in @mask whenever MAY_APPEND, MAY_CREATE_FILE, or
- * MAY_CREATE_DIR are set. That way, file systems that don't support these
- * permissions will check for MAY_WRITE instead.
+ * MAY_WRITE must be set in @mask whenever MAY_APPEND, MAY_CREATE_FILE,
+ * MAY_CREATE_DIR, or MAY_DELETE_CHILD are set. That way, file systems that
+ * don't support these permissions will check for MAY_WRITE instead.
*/
int inode_permission(struct inode *inode, int mask)
{
@@ -2780,14 +2780,20 @@ static int may_delete_or_replace(struct inode *dir, struct dentry *victim,
BUG_ON(victim->d_parent->d_inode != dir);
audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);

- error = inode_permission(dir, mask);
+ error = inode_permission(dir, mask | MAY_WRITE | MAY_DELETE_CHILD);
+ if (!error && check_sticky(dir, inode))
+ error = -EPERM;
+ if (error && IS_RICHACL(inode) &&
+ inode_permission(inode, MAY_DELETE_SELF) == 0 &&
+ inode_permission(dir, mask) == 0)
+ error = 0;
if (error)
return error;
if (IS_APPEND(dir))
return -EPERM;

- if (check_sticky(dir, inode) || IS_APPEND(inode) ||
- IS_IMMUTABLE(inode) || IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
+ if (IS_APPEND(inode) || IS_IMMUTABLE(inode) ||
+ IS_SWAPFILE(inode) || HAS_UNMAPPED_ID(inode))
return -EPERM;
if (isdir) {
if (!d_is_dir(victim))
@@ -2805,7 +2811,7 @@ static int may_delete_or_replace(struct inode *dir, struct dentry *victim,

static int may_delete(struct inode *dir, struct dentry *victim, bool isdir)
{
- return may_delete_or_replace(dir, victim, isdir, MAY_WRITE | MAY_EXEC);
+ return may_delete_or_replace(dir, victim, isdir, MAY_EXEC);
}

static int may_replace(struct inode *dir, struct dentry *victim, bool isdir)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 99bbd6c..907869d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -86,6 +86,8 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
#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
--
2.7.4
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