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Diffstat (limited to 'fs/xattr.c')
-rw-r--r--fs/xattr.c61
1 files changed, 57 insertions, 4 deletions
diff --git a/fs/xattr.c b/fs/xattr.c
index fee804e..80eca7d 100644
--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -20,6 +20,47 @@
#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)
@@ -27,6 +68,10 @@ vfs_setxattr(struct dentry *dentry, char *name, void *value,
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)
@@ -40,8 +85,8 @@ vfs_setxattr(struct dentry *dentry, char *name, void *value,
size, flags);
}
} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
- sizeof XATTR_SECURITY_PREFIX - 1)) {
- const char *suffix = name + sizeof XATTR_SECURITY_PREFIX - 1;
+ XATTR_SECURITY_PREFIX_LEN)) {
+ const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
error = security_inode_setsecurity(inode, suffix, value,
size, flags);
if (!error)
@@ -59,6 +104,10 @@ 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;
@@ -69,8 +118,8 @@ vfs_getxattr(struct dentry *dentry, char *name, void *value, size_t size)
error = -EOPNOTSUPP;
if (!strncmp(name, XATTR_SECURITY_PREFIX,
- sizeof XATTR_SECURITY_PREFIX - 1)) {
- const char *suffix = name + sizeof XATTR_SECURITY_PREFIX - 1;
+ XATTR_SECURITY_PREFIX_LEN)) {
+ const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
int ret = security_inode_getsecurity(inode, suffix, value,
size, error);
/*
@@ -94,6 +143,10 @@ vfs_removexattr(struct dentry *dentry, char *name)
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;
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