Merge patch series "fscache/cachefiles: Some bugfixes"

Zizhi Wo <wozizhi@huawei.com> says:

This patchset mainly includes 5 fix patches about fscache/cachefiles.
The first patch fixes an issue with the incorrect return length, and the
fourth patch addresses a null pointer dereference issue with file.

* patches from https://lore.kernel.org/r/20241107110649.3980193-1-wozizhi@huawei.com:
  netfs/fscache: Add a memory barrier for FSCACHE_VOLUME_CREATING
  cachefiles: Fix NULL pointer dereference in object->file
  cachefiles: Clean up in cachefiles_commit_tmpfile()
  cachefiles: Fix missing pos updates in cachefiles_ondemand_fd_write_iter()
  cachefiles: Fix incorrect length return value in cachefiles_ondemand_fd_write_iter()

Link: https://lore.kernel.org/r/20241107110649.3980193-1-wozizhi@huawei.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

4 files changed, 40 insertions, 20 deletions

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 35ba2117a6f6..3e63cfe15874 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -327,6 +327,8 @@ static void cachefiles_commit_object(struct cachefiles_object *object,
 static void cachefiles_clean_up_object(struct cachefiles_object *object,
 				       struct cachefiles_cache *cache)
 {
+	struct file *file;
+
 	if (test_bit(FSCACHE_COOKIE_RETIRED, &object->cookie->flags)) {
 		if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 			cachefiles_see_object(object, cachefiles_obj_see_clean_delete);
@@ -342,10 +344,14 @@ static void cachefiles_clean_up_object(struct cachefiles_object *object,
 	}
 
 	cachefiles_unmark_inode_in_use(object, object->file);
-	if (object->file) {
-		fput(object->file);
-		object->file = NULL;
-	}
+
+	spin_lock(&object->lock);
+	file = object->file;
+	object->file = NULL;
+	spin_unlock(&object->lock);
+
+	if (file)
+		fput(file);
 }
 
 /*
diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 2b3f9935dbb4..7cf59713f0f7 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -691,11 +691,6 @@ bool cachefiles_commit_tmpfile(struct cachefiles_cache *cache,
 	}
 
 	if (!d_is_negative(dentry)) {
-		if (d_backing_inode(dentry) == file_inode(object->file)) {
-			success = true;
-			goto out_dput;
-		}
-
 		ret = cachefiles_unlink(volume->cache, object, fan, dentry,
 					FSCACHE_OBJECT_IS_STALE);
 		if (ret < 0)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 470c96658385..fe3de9ad57bf 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -60,26 +60,36 @@ static ssize_t cachefiles_ondemand_fd_write_iter(struct kiocb *kiocb,
 {
 	struct cachefiles_object *object = kiocb->ki_filp->private_data;
 	struct cachefiles_cache *cache = object->volume->cache;
-	struct file *file = object->file;
-	size_t len = iter->count;
+	struct file *file;
+	size_t len = iter->count, aligned_len = len;
 	loff_t pos = kiocb->ki_pos;
 	const struct cred *saved_cred;
 	int ret;
 
-	if (!file)
+	spin_lock(&object->lock);
+	file = object->file;
+	if (!file) {
+		spin_unlock(&object->lock);
 		return -ENOBUFS;
+	}
+	get_file(file);
+	spin_unlock(&object->lock);
 
 	cachefiles_begin_secure(cache, &saved_cred);
-	ret = __cachefiles_prepare_write(object, file, &pos, &len, len, true);
+	ret = __cachefiles_prepare_write(object, file, &pos, &aligned_len, len, true);
 	cachefiles_end_secure(cache, saved_cred);
 	if (ret < 0)
-		return ret;
+		goto out;
 
 	trace_cachefiles_ondemand_fd_write(object, file_inode(file), pos, len);
 	ret = __cachefiles_write(object, file, pos, iter, NULL, NULL);
-	if (!ret)
+	if (!ret) {
 		ret = len;
+		kiocb->ki_pos += ret;
+	}
 
+out:
+	fput(file);
 	return ret;
 }
 
@@ -87,12 +97,22 @@ static loff_t cachefiles_ondemand_fd_llseek(struct file *filp, loff_t pos,
 					    int whence)
 {
 	struct cachefiles_object *object = filp->private_data;
-	struct file *file = object->file;
+	struct file *file;
+	loff_t ret;
 
-	if (!file)
+	spin_lock(&object->lock);
+	file = object->file;
+	if (!file) {
+		spin_unlock(&object->lock);
 		return -ENOBUFS;
+	}
+	get_file(file);
+	spin_unlock(&object->lock);
 
-	return vfs_llseek(file, pos, whence);
+	ret = vfs_llseek(file, pos, whence);
+	fput(file);
+
+	return ret;
 }
 
 static long cachefiles_ondemand_fd_ioctl(struct file *filp, unsigned int ioctl,
diff --git a/fs/netfs/fscache_volume.c b/fs/netfs/fscache_volume.c
index cb75c07b5281..ced14ac78cc1 100644
--- a/fs/netfs/fscache_volume.c
+++ b/fs/netfs/fscache_volume.c
@@ -322,8 +322,7 @@ maybe_wait:
 	}
 	return;
 no_wait:
-	clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
-	wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
+	clear_and_wake_up_bit(FSCACHE_VOLUME_CREATING, &volume->flags);
 }
 
 /*