From 0dbf68a3e2f87216e834403eb4ac61d455bf7c50 Mon Sep 17 00:00:00 2001 From: Andy Whitcroft Date: Tue, 1 May 2012 16:17:51 +0100 Subject: UBUNTU: ubuntu: overlayfs -- inode_only_permission: export inode level permissions checks We need to be able to check inode permissions (but not filesystem implied permissions) for stackable filesystems. Now that permissions involve checking with the security LSM, cgroups and basic inode permissions it is easy to miss a key permission check and introduce a security vunerability. Expose a new interface for these checks. Signed-off-by: Andy Whitcroft Signed-off-by: Miklos Szeredi --- fs/namei.c | 48 +++++++++++++++++++++++++++++++----------------- include/linux/fs.h | 1 + 2 files changed, 32 insertions(+), 17 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index f09edf3eeef..caf090c4862 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -314,6 +314,36 @@ static inline int do_inode_permission(struct inode *inode, int mask) return generic_permission(inode, mask); } +/** + * inode_only_permission - check access rights to a given inode only + * @inode: inode to check permissions on + * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...) + * + * Uses to check read/write/execute permissions on an inode directly, we do + * not check filesystem permissions. + */ +int inode_only_permission(struct inode *inode, int mask) +{ + int retval; + + /* + * Nobody gets write access to an immutable file. + */ + if (unlikely(mask & MAY_WRITE) && IS_IMMUTABLE(inode)) + return -EACCES; + + retval = do_inode_permission(inode, mask); + if (retval) + return retval; + + retval = devcgroup_inode_permission(inode, mask); + if (retval) + return retval; + + return security_inode_permission(inode, mask); +} +EXPORT_SYMBOL(inode_only_permission); + /** * inode_permission - check for access rights to a given inode * @inode: inode to check permission on @@ -328,8 +358,6 @@ static inline int do_inode_permission(struct inode *inode, int mask) */ int inode_permission(struct inode *inode, int mask) { - int retval; - if (unlikely(mask & MAY_WRITE)) { umode_t mode = inode->i_mode; @@ -339,23 +367,9 @@ int inode_permission(struct inode *inode, int mask) if (IS_RDONLY(inode) && (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) return -EROFS; - - /* - * Nobody gets write access to an immutable file. - */ - if (IS_IMMUTABLE(inode)) - return -EACCES; } - retval = do_inode_permission(inode, mask); - if (retval) - return retval; - - retval = devcgroup_inode_permission(inode, mask); - if (retval) - return retval; - - return security_inode_permission(inode, mask); + return inode_only_permission(inode, mask); } /** diff --git a/include/linux/fs.h b/include/linux/fs.h index 49b86cf0564..e99bb48293d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2263,6 +2263,7 @@ extern sector_t bmap(struct inode *, sector_t); #endif extern int notify_change(struct dentry *, struct iattr *); extern int inode_permission(struct inode *, int); +extern int inode_only_permission(struct inode *, int); extern int generic_permission(struct inode *, int); static inline bool execute_ok(struct inode *inode) -- cgit v1.2.3