Normally, deleting a file requires write and execute access to the parent
directory. With Richacls, a process with MAY_DELETE_SELF access to a file may
delete the file even without write access to the parent directory.
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 itelf.
The MAY_DELETE_SELF permission does not override the sticky directory check.
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/namei.c | 15 +++++++++++----
include/linux/fs.h | 2 ++
2 files changed, 13 insertions(+), 4 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index a8bc030..a8d1674 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -455,7 +455,7 @@ 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)
{
@@ -2452,7 +2452,7 @@ static int may_delete(struct inode *dir, struct dentry *victim,
bool isdir, bool replace)
{
struct inode *inode = victim->d_inode;
- int error, mask = MAY_WRITE | MAY_EXEC;
+ int error, mask = MAY_EXEC;
if (d_is_negative(victim))
return -ENOENT;
@@ -2462,8 +2462,15 @@ static int may_delete(struct inode *dir, struct dentry *victim,
audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
if (replace)
- mask |= isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE;
- error = inode_permission(dir, mask);
+ mask |= MAY_WRITE | (isdir ? MAY_CREATE_DIR : MAY_CREATE_FILE);
+ error = inode_permission(dir, mask | MAY_WRITE | MAY_DELETE_CHILD);
+ if (error && IS_RICHACL(inode)) {
+ /* Deleting is also permitted with MAY_EXEC on the directory
+ * and MAY_DELETE_SELF on the inode. */
+ if (!inode_permission(inode, MAY_DELETE_SELF) &&
+ !inode_permission(dir, mask))
+ error = 0;
+ }
if (error)
return error;
if (IS_APPEND(dir))
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2cced7c..5701f90 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -82,6 +82,8 @@ typedef void (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
--
2.1.0
--
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