diff mbox

[-V6,09/26] vfs: Add delete child and delete self permission flags

Message ID 1315243548-18664-10-git-send-email-aneesh.kumar@linux.vnet.ibm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Aneesh Kumar K.V Sept. 5, 2011, 5:25 p.m. UTC 
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         |   41 +++++++++++++++++++++++++++--------------
 include/linux/fs.h |    2 ++
 2 files changed, 29 insertions(+), 14 deletions(-)

Comments

J. Bruce Fields Sept. 7, 2011, 8:39 p.m. UTC | #1 
On Mon, Sep 05, 2011 at 10:55:31PM +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         |   41 +++++++++++++++++++++++++++--------------
>  include/linux/fs.h |    2 ++
>  2 files changed, 29 insertions(+), 14 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index d52a4cd..eacb530 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)
>  {
> @@ -1862,7 +1862,7 @@ 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;
>  }
>  
>  /*
> @@ -1884,30 +1884,43 @@ 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;
> +	int mask, error, is_sticky;
> +	struct inode *inode = victim->d_inode;
>  
> -	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)
> +		mask |= S_ISDIR(inode->i_mode) ?
> +			MAY_CREATE_DIR : MAY_CREATE_FILE;

I'm having trouble understanding this next bit:

> +	is_sticky = check_sticky(dir, inode);
> +	error = inode_permission(dir, mask);
> +	if ((error || is_sticky) && IS_RICHACL(inode) &&
> +	    !inode_permission(dir, mask & ~(MAY_WRITE | MAY_DELETE_CHILD)) &&
> +	    !inode_permission(inode, MAY_DELETE_SELF))
> +		error = 0;

OK, so we can ignore the lack of write or delete permissions on the
parent if we have delete_self permissions on the child.  I guess that's
right.

Why the "|| is_sticky" above?

Is there some less complicated why to write this?

--b.

> +	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;
> @@ -2614,7 +2627,7 @@ 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;
> @@ -2707,7 +2720,7 @@ 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;
> @@ -3101,14 +3114,14 @@ 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 8707f43..c5c98c5 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
> -- 
> 1.7.4.1
> 
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Aneesh Kumar K.V Sept. 8, 2011, 9:30 a.m. UTC | #2 
On Wed, 7 Sep 2011 16:39:16 -0400, "J. Bruce Fields" <bfields@fieldses.org> wrote:
> On Mon, Sep 05, 2011 at 10:55:31PM +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         |   41 +++++++++++++++++++++++++++--------------
> >  include/linux/fs.h |    2 ++
> >  2 files changed, 29 insertions(+), 14 deletions(-)
> > 
> > diff --git a/fs/namei.c b/fs/namei.c
> > index d52a4cd..eacb530 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)
> >  {
> > @@ -1862,7 +1862,7 @@ 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;
> >  }
> >  
> >  /*
> > @@ -1884,30 +1884,43 @@ 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;
> > +	int mask, error, is_sticky;
> > +	struct inode *inode = victim->d_inode;
> >  
> > -	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)
> > +		mask |= S_ISDIR(inode->i_mode) ?
> > +			MAY_CREATE_DIR : MAY_CREATE_FILE;
> 
> I'm having trouble understanding this next bit:
> 
> > +	is_sticky = check_sticky(dir, inode);
> > +	error = inode_permission(dir, mask);
> > +	if ((error || is_sticky) && IS_RICHACL(inode) &&
> > +	    !inode_permission(dir, mask & ~(MAY_WRITE | MAY_DELETE_CHILD)) &&
> > +	    !inode_permission(inode, MAY_DELETE_SELF))
> > +		error = 0;
> 
> OK, so we can ignore the lack of write or delete permissions on the
> parent if we have delete_self permissions on the child.  I guess that's
> right.
> 
> Why the "|| is_sticky" above?
> 
> Is there some less complicated why to write this?

we removed the ns_capable check out of check_sticky, because we don't
want to do capability check when richacl allows access. We also want to
make sure that even if mode bits allow access (inode_permission(dir, mask))
if sticky bit is set we do additional check.


-aneesh
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diff mbox

Patch

diff --git a/fs/namei.c b/fs/namei.c
index d52a4cd..eacb530 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)
 {
@@ -1862,7 +1862,7 @@  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;
 }
 
 /*
@@ -1884,30 +1884,43 @@  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;
+	int mask, error, is_sticky;
+	struct inode *inode = victim->d_inode;
 
-	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)
+		mask |= S_ISDIR(inode->i_mode) ?
+			MAY_CREATE_DIR : MAY_CREATE_FILE;
+	is_sticky = check_sticky(dir, inode);
+	error = inode_permission(dir, mask);
+	if ((error || is_sticky) && IS_RICHACL(inode) &&
+	    !inode_permission(dir, mask & ~(MAY_WRITE | MAY_DELETE_CHILD)) &&
+	    !inode_permission(inode, MAY_DELETE_SELF))
+		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;
@@ -2614,7 +2627,7 @@  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;
@@ -2707,7 +2720,7 @@  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;
@@ -3101,14 +3114,14 @@  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 8707f43..c5c98c5 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