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authorDavid Howells <dhowells@redhat.com>2012-06-25 12:55:46 +0100
committerAl Viro <viro@zeniv.linux.org.uk>2012-07-14 16:38:36 +0400
commit0bdaea9017b9d2b9996e153a71ee03555969b80e (patch)
tree112d8c8a2f0adb0b68356b1e39209454a7a6ea71
parent9249e17fe094d853d1ef7475dd559a2cc7e23d42 (diff)
VFS: Split inode_permission()
Split inode_permission() into inode- and superblock-dependent parts. This is aimed at unionmounts where the superblock from the upper layer has to be checked rather than the superblock from the lower layer as the upper layer may be writable, thus allowing an unwritable file from the lower layer to be copied up and modified. Original-author: Valerie Aurora <vaurora@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> (Further development) Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/internal.h5
-rw-r--r--fs/namei.c66
2 files changed, 54 insertions, 17 deletions
diff --git a/fs/internal.h b/fs/internal.h
index 8a9f5fa840f..a6fd56c68b1 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -42,6 +42,11 @@ static inline int __sync_blockdev(struct block_device *bdev, int wait)
extern void __init chrdev_init(void);
/*
+ * namei.c
+ */
+extern int __inode_permission(struct inode *, int);
+
+/*
* namespace.c
*/
extern int copy_mount_options(const void __user *, unsigned long *);
diff --git a/fs/namei.c b/fs/namei.c
index c6dcb4c8f86..1b647468769 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -315,31 +315,22 @@ static inline int do_inode_permission(struct inode *inode, int mask)
}
/**
- * inode_permission - check for access rights to a given inode
- * @inode: inode to check permission on
- * @mask: right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
+ * __inode_permission - Check for access rights to a given inode
+ * @inode: Inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
*
- * Used to check for read/write/execute permissions on an inode.
- * We use "fsuid" for this, letting us set arbitrary permissions
- * for filesystem access without changing the "normal" uids which
- * are used for other things.
+ * Check for read/write/execute permissions on an inode.
*
* When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
+ *
+ * This does not check for a read-only file system. You probably want
+ * inode_permission().
*/
-int 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;
-
- /*
- * Nobody gets write access to a read-only fs.
- */
- if (IS_RDONLY(inode) &&
- (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
- return -EROFS;
-
/*
* Nobody gets write access to an immutable file.
*/
@@ -359,6 +350,47 @@ int inode_permission(struct inode *inode, int mask)
}
/**
+ * sb_permission - Check superblock-level permissions
+ * @sb: Superblock of inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Separate out file-system wide checks from inode-specific permission checks.
+ */
+static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
+{
+ if (unlikely(mask & MAY_WRITE)) {
+ umode_t mode = inode->i_mode;
+
+ /* Nobody gets write access to a read-only fs. */
+ if ((sb->s_flags & MS_RDONLY) &&
+ (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
+ return -EROFS;
+ }
+ return 0;
+}
+
+/**
+ * inode_permission - Check for access rights to a given inode
+ * @inode: Inode to check permission on
+ * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
+ *
+ * Check for read/write/execute permissions on an inode. We use fs[ug]id for
+ * this, letting us set arbitrary permissions for filesystem access without
+ * changing the "normal" UIDs which are used for other things.
+ *
+ * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
+ */
+int inode_permission(struct inode *inode, int mask)
+{
+ int retval;
+
+ retval = sb_permission(inode->i_sb, inode, mask);
+ if (retval)
+ return retval;
+ return __inode_permission(inode, mask);
+}
+
+/**
* path_get - get a reference to a path
* @path: path to get the reference to
*