diff options
Diffstat (limited to 'fs/xattr.c')
| -rw-r--r-- | fs/xattr.c | 199 |
1 files changed, 146 insertions, 53 deletions
diff --git a/fs/xattr.c b/fs/xattr.c index bcc2156d4d2..80eca7d3d69 100644 --- a/fs/xattr.c +++ b/fs/xattr.c @@ -19,6 +19,149 @@ #include <linux/fsnotify.h> #include <asm/uaccess.h> + +/* + * Check permissions for extended attribute access. This is a bit complicated + * because different namespaces have very different rules. + */ +static int +xattr_permission(struct inode *inode, const char *name, int mask) +{ + /* + * We can never set or remove an extended attribute on a read-only + * filesystem or on an immutable / append-only inode. + */ + if (mask & MAY_WRITE) { + if (IS_RDONLY(inode)) + return -EROFS; + if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) + return -EPERM; + } + + /* + * No restriction for security.* and system.* from the VFS. Decision + * on these is left to the underlying filesystem / security module. + */ + if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) || + !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN)) + return 0; + + /* + * The trusted.* namespace can only accessed by a privilegued user. + */ + if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) + return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM); + + if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) { + if (!S_ISREG(inode->i_mode) && + (!S_ISDIR(inode->i_mode) || inode->i_mode & S_ISVTX)) + return -EPERM; + } + + return permission(inode, mask, NULL); +} + +int +vfs_setxattr(struct dentry *dentry, char *name, void *value, + size_t size, int flags) +{ + struct inode *inode = dentry->d_inode; + int error; + + error = xattr_permission(inode, name, MAY_WRITE); + if (error) + return error; + + mutex_lock(&inode->i_mutex); + error = security_inode_setxattr(dentry, name, value, size, flags); + if (error) + goto out; + error = -EOPNOTSUPP; + if (inode->i_op->setxattr) { + error = inode->i_op->setxattr(dentry, name, value, size, flags); + if (!error) { + fsnotify_xattr(dentry); + security_inode_post_setxattr(dentry, name, value, + size, flags); + } + } else if (!strncmp(name, XATTR_SECURITY_PREFIX, + XATTR_SECURITY_PREFIX_LEN)) { + const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; + error = security_inode_setsecurity(inode, suffix, value, + size, flags); + if (!error) + fsnotify_xattr(dentry); + } +out: + mutex_unlock(&inode->i_mutex); + return error; +} +EXPORT_SYMBOL_GPL(vfs_setxattr); + +ssize_t +vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size) +{ + struct inode *inode = dentry->d_inode; + int error; + + error = xattr_permission(inode, name, MAY_READ); + if (error) + return error; + + error = security_inode_getxattr(dentry, name); + if (error) + return error; + + if (inode->i_op->getxattr) + error = inode->i_op->getxattr(dentry, name, value, size); + else + error = -EOPNOTSUPP; + + if (!strncmp(name, XATTR_SECURITY_PREFIX, + XATTR_SECURITY_PREFIX_LEN)) { + const char *suffix = name + XATTR_SECURITY_PREFIX_LEN; + int ret = security_inode_getsecurity(inode, suffix, value, + size, error); + /* + * Only overwrite the return value if a security module + * is actually active. + */ + if (ret != -EOPNOTSUPP) + error = ret; + } + + return error; +} +EXPORT_SYMBOL_GPL(vfs_getxattr); + +int +vfs_removexattr(struct dentry *dentry, char *name) +{ + struct inode *inode = dentry->d_inode; + int error; + + if (!inode->i_op->removexattr) + return -EOPNOTSUPP; + + error = xattr_permission(inode, name, MAY_WRITE); + if (error) + return error; + + error = security_inode_removexattr(dentry, name); + if (error) + return error; + + mutex_lock(&inode->i_mutex); + error = inode->i_op->removexattr(dentry, name); + mutex_unlock(&inode->i_mutex); + + if (!error) + fsnotify_xattr(dentry); + return error; +} +EXPORT_SYMBOL_GPL(vfs_removexattr); + + /* * Extended attribute SET operations */ @@ -51,29 +194,7 @@ setxattr(struct dentry *d, char __user *name, void __user *value, } } - down(&d->d_inode->i_sem); - error = security_inode_setxattr(d, kname, kvalue, size, flags); - if (error) - goto out; - error = -EOPNOTSUPP; - if (d->d_inode->i_op && d->d_inode->i_op->setxattr) { - error = d->d_inode->i_op->setxattr(d, kname, kvalue, - size, flags); - if (!error) { - fsnotify_xattr(d); - security_inode_post_setxattr(d, kname, kvalue, - size, flags); - } - } else if (!strncmp(kname, XATTR_SECURITY_PREFIX, - sizeof XATTR_SECURITY_PREFIX - 1)) { - const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1; - error = security_inode_setsecurity(d->d_inode, suffix, kvalue, - size, flags); - if (!error) - fsnotify_xattr(d); - } -out: - up(&d->d_inode->i_sem); + error = vfs_setxattr(d, kname, kvalue, size, flags); kfree(kvalue); return error; } @@ -147,22 +268,7 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) return -ENOMEM; } - error = security_inode_getxattr(d, kname); - if (error) - goto out; - error = -EOPNOTSUPP; - if (d->d_inode->i_op && d->d_inode->i_op->getxattr) - error = d->d_inode->i_op->getxattr(d, kname, kvalue, size); - - if (!strncmp(kname, XATTR_SECURITY_PREFIX, - sizeof XATTR_SECURITY_PREFIX - 1)) { - const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1; - int rv = security_inode_getsecurity(d->d_inode, suffix, kvalue, - size, error); - /* Security module active: overwrite error value */ - if (rv != -EOPNOTSUPP) - error = rv; - } + error = vfs_getxattr(d, kname, kvalue, size); if (error > 0) { if (size && copy_to_user(value, kvalue, error)) error = -EFAULT; @@ -171,7 +277,6 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) than XATTR_SIZE_MAX bytes. Not possible. */ error = -E2BIG; } -out: kfree(kvalue); return error; } @@ -318,19 +423,7 @@ removexattr(struct dentry *d, char __user *name) if (error < 0) return error; - error = -EOPNOTSUPP; - if (d->d_inode->i_op && d->d_inode->i_op->removexattr) { - error = security_inode_removexattr(d, kname); - if (error) - goto out; - down(&d->d_inode->i_sem); - error = d->d_inode->i_op->removexattr(d, kname); - up(&d->d_inode->i_sem); - if (!error) - fsnotify_xattr(d); - } -out: - return error; + return vfs_removexattr(d, kname); } asmlinkage long |