[PATCH 06/10] cachefiles, erofs: Fix NULL deref in when cachefiles is not doing ondemand-mode

[David Howells <dhowells@xxxxxxxxxx>]

cachefiles_ondemand_init_object() as called from cachefiles_open_file() and
cachefiles_create_tmpfile() does not check if object->ondemand is set
before dereferencing it, leading to an oops something like:

	RIP: 0010:cachefiles_ondemand_init_object+0x9/0x41
	...
	Call Trace:
	 <TASK>
	 cachefiles_open_file+0xc9/0x187
	 cachefiles_lookup_cookie+0x122/0x2be
	 fscache_cookie_state_machine+0xbe/0x32b
	 fscache_cookie_worker+0x1f/0x2d
	 process_one_work+0x136/0x208
	 process_scheduled_works+0x3a/0x41
	 worker_thread+0x1a2/0x1f6
	 kthread+0xca/0xd2
	 ret_from_fork+0x21/0x33

Fix this by making the calls to cachefiles_ondemand_init_object()
conditional.

Fixes: 3c5ecfe16e76 ("cachefiles: extract ondemand info field from cachefiles_object")
Reported-by: Marc Dionne <marc.dionne@xxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Gao Xiang <xiang@xxxxxxxxxx>
cc: Chao Yu <chao@xxxxxxxxxx>
cc: Yue Hu <huyue2@xxxxxxxxxxx>
cc: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
cc: linux-erofs@xxxxxxxxxxxxxxxx
cc: netfs@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
 fs/cachefiles/namei.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 7ade836beb58..180594d24c44 100644
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -473,9 +473,11 @@ struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 	if (!cachefiles_mark_inode_in_use(object, file_inode(file)))
 		WARN_ON(1);
 
-	ret = cachefiles_ondemand_init_object(object);
-	if (ret < 0)
-		goto err_unuse;
+	if (object->ondemand) {
+		ret = cachefiles_ondemand_init_object(object);
+		if (ret < 0)
+			goto err_unuse;
+	}
 
 	ni_size = object->cookie->object_size;
 	ni_size = round_up(ni_size, CACHEFILES_DIO_BLOCK_SIZE);
@@ -579,9 +581,11 @@ static bool cachefiles_open_file(struct cachefiles_object *object,
 	}
 	_debug("file -> %pd positive", dentry);
 
-	ret = cachefiles_ondemand_init_object(object);
-	if (ret < 0)
-		goto error_fput;
+	if (object->ondemand) {
+		ret = cachefiles_ondemand_init_object(object);
+		if (ret < 0)
+			goto error_fput;
+	}
 
 	ret = cachefiles_check_auxdata(object, file);
 	if (ret < 0)