Merge tag 'vfs-7.2-rc1.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull simple_xattr updates from Christian Brauner:
 "This reworks the simple xattr api to make it more efficient and easier
  to use for all consumers.

  The simple_xattr hash table moves from the inode into a per-superblock
  cache, removing the per-inode overhead for the common case of few or
  no xattrs. The interface now passes struct simple_xattrs ** so lazy
  allocation is handled internally instead of by every caller, kernfs
  xattr operations on kernfs nodes shared between multiple superblocks
  are properly serialized, and tmpfs constructs "security.foo" xattr
  names with kasprintf() instead of kmalloc() plus two memcpy()s.

  A follow-up fix links kernfs nodes to their parent before the LSM init
  hook runs: with the per-sb cache kernfs_xattr_set() computes the cache
  via kernfs_root(kn), which faulted on a freshly allocated node when
  selinux_kernfs_init_security() called into it - reproducible as a NULL
  pointer dereference on the first cgroup mkdir on SELinux-enabled
  systems.

  On top of this bpffs gains support for trusted.* and security.* xattrs
  so that user space and BPF LSM programs can attach metadata - for
  example a content hash or a security label - to pinned objects and
  directories and inspect it uniformly like on other filesystems. The
  store is in-memory and non-persistent, living only for the lifetime of
  the mount like everything else in bpffs"

* tag 'vfs-7.2-rc1.xattr' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  bpf: Add simple xattr support to bpffs
  kernfs: link kn to its parent before the LSM init hook
  simpe_xattr: use per-sb cache
  simple_xattr: change interface to pass struct simple_xattrs **
  tmpfs: simplify constructing "security.foo" xattr names
  kernfs: fix xattr race condition with multiple superblocks

1 files changed, 9 insertions, 21 deletions

diff --git a/net/socket.c b/net/socket.c
index c2698a1441a7..f51bdcbaa43f 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -310,8 +310,10 @@ efault_end:
 
 static struct kmem_cache *sock_inode_cachep __ro_after_init;
 
+static struct simple_xattr_cache sockfs_xa_cache;
+
 struct sockfs_inode {
-	struct simple_xattrs *xattrs;
+	struct list_head xattrs;
 	struct simple_xattr_limits xattr_limits;
 	struct socket_alloc;
 };
@@ -328,7 +330,7 @@ static struct inode *sock_alloc_inode(struct super_block *sb)
 	si = alloc_inode_sb(sb, sock_inode_cachep, GFP_KERNEL);
 	if (!si)
 		return NULL;
-	si->xattrs = NULL;
+	INIT_LIST_HEAD_RCU(&si->xattrs);
 	simple_xattr_limits_init(&si->xattr_limits);
 
 	init_waitqueue_head(&si->socket.wq.wait);
@@ -347,12 +349,8 @@ static struct inode *sock_alloc_inode(struct super_block *sb)
 static void sock_evict_inode(struct inode *inode)
 {
 	struct sockfs_inode *si = SOCKFS_I(inode);
-	struct simple_xattrs *xattrs = si->xattrs;
 
-	if (xattrs) {
-		simple_xattrs_free(xattrs, NULL);
-		kfree(xattrs);
-	}
+	simple_xattrs_free(&sockfs_xa_cache, &si->xattrs, NULL);
 	clear_inode(inode);
 }
 
@@ -443,13 +441,9 @@ static int sockfs_user_xattr_get(const struct xattr_handler *handler,
 				 const char *suffix, void *value, size_t size)
 {
 	const char *name = xattr_full_name(handler, suffix);
-	struct simple_xattrs *xattrs;
-
-	xattrs = READ_ONCE(SOCKFS_I(inode)->xattrs);
-	if (!xattrs)
-		return -ENODATA;
+	struct sockfs_inode *si = SOCKFS_I(inode);
 
-	return simple_xattr_get(xattrs, name, value, size);
+	return simple_xattr_get(&sockfs_xa_cache, &si->xattrs, name, value, size);
 }
 
 static int sockfs_user_xattr_set(const struct xattr_handler *handler,
@@ -460,13 +454,8 @@ static int sockfs_user_xattr_set(const struct xattr_handler *handler,
 {
 	const char *name = xattr_full_name(handler, suffix);
 	struct sockfs_inode *si = SOCKFS_I(inode);
-	struct simple_xattrs *xattrs;
-
-	xattrs = simple_xattrs_lazy_alloc(&si->xattrs, value, flags);
-	if (IS_ERR_OR_NULL(xattrs))
-		return PTR_ERR(xattrs);
 
-	return simple_xattr_set_limited(xattrs, &si->xattr_limits,
+	return simple_xattr_set_limited(&sockfs_xa_cache, &si->xattrs, &si->xattr_limits,
 					name, value, size, flags);
 }
 
@@ -635,8 +624,7 @@ static ssize_t sockfs_listxattr(struct dentry *dentry, char *buffer,
 	struct sockfs_inode *si = SOCKFS_I(d_inode(dentry));
 	ssize_t len, used;
 
-	len = simple_xattr_list(d_inode(dentry), READ_ONCE(si->xattrs),
-				buffer, size);
+	len = simple_xattr_list(d_inode(dentry), &si->xattrs, buffer, size);
 	if (len < 0)
 		return len;