simple_xattr: change interface to pass struct simple_xattrs **

Change the simple_xattr API to accept pointer-to-pointer (struct
simple_xattrs **) instead of pointer.  This allows the functions to handle
lazy allocation internally without requiring callers to use
simple_xattrs_lazy_alloc().

The simple_xattr_set(), simple_xattr_set_limited() and simple_xattr_add()
functions now handle allocation when xattrs is NULL.  simple_xattrs_free()
now also frees the xattrs structure itself and sets the pointer to NULL.

This simplifies callers and removes the need for most callers to explicitly
manage xattrs allocation and lifetime.

In shmem_initxattrs(), the total required space for all initial xattrs
(ispace) is pre-calculated and deducted from sbinfo->free_ispace.

Since this patch modifies the function to add new xattrs directly to the
inode's &info->xattrs list rather than using a local temporary variable, a
failure means that the partially populated info->xattrs list remains
attached to the inode.

When the VFS caller handles the -ENOMEM error, it drops the newly created
inode via iput(), shmem_free_inode() adds freed to sbinfo->free_ispace a
second time, permanently inflating the tmpfs free space quota.

Fix by substracting already added xattrs from ispace.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Link: https://patch.msgid.link/20260605135322.2632068-4-mszeredi@redhat.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

1 files changed, 5 insertions, 19 deletions

diff --git a/net/socket.c b/net/socket.c
index 22a412fdec07..d3597c858345 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -347,12 +347,8 @@ 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(&si->xattrs, NULL);
 	clear_inode(inode);
 }
 
@@ -443,13 +439,9 @@ 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(&si->xattrs, name, value, size);
 }
 
 static int sockfs_user_xattr_set(const struct xattr_handler *handler,
@@ -460,13 +452,8 @@ 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(&si->xattrs, &si->xattr_limits,
 					name, value, size, flags);
 }
 
@@ -635,8 +622,7 @@ 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;