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

[David Howells]

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.dio...@auristor.com>
Signed-off-by: David Howells <dhowe...@redhat.com>
cc: Gao Xiang <xi...@kernel.org>
cc: Chao Yu <c...@kernel.org>
cc: Yue Hu <huy...@coolpad.com>
cc: Jeffle Xu <jeffl...@linux.alibaba.com>
cc: linux-erofs@lists.ozlabs.org
cc: ne...@lists.linux.dev
cc: linux-fsde...@vger.kernel.org
---
 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)