diff mbox series

[v3,7/9] cachefiles: wait for ondemand_object_worker to finish when dropping object

Message ID 20240628062930.2467993-8-libaokun@huaweicloud.com (mailing list archive)
State New
Headers show
Series cachefiles: random bugfixes | expand

Commit Message

Baokun Li June 28, 2024, 6:29 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

When queuing ondemand_object_worker() to re-open the object,
cachefiles_object is not pinned. The cachefiles_object may be freed when
the pending read request is completed intentionally and the related
erofs is umounted. If ondemand_object_worker() runs after the object is
freed, it will incur use-after-free problem as shown below.

process A  processs B  process C  process D

cachefiles_ondemand_send_req()
// send a read req X
// wait for its completion

           // close ondemand fd
           cachefiles_ondemand_fd_release()
           // set object as CLOSE

                       cachefiles_ondemand_daemon_read()
                       // set object as REOPENING
                       queue_work(fscache_wq, &info->ondemand_work)

                                // close /dev/cachefiles
                                cachefiles_daemon_release
                                cachefiles_flush_reqs
                                complete(&req->done)

// read req X is completed
// umount the erofs fs
cachefiles_put_object()
// object will be freed
cachefiles_ondemand_deinit_obj_info()
kmem_cache_free(object)
                       // both info and object are freed
                       ondemand_object_worker()

When dropping an object, it is no longer necessary to reopen the object,
so use cancel_work_sync() to cancel or wait for ondemand_object_worker()
to finish.

Fixes: 0a7e54c1959c ("cachefiles: resend an open request if the read request's object is closed")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
---
 fs/cachefiles/ondemand.c | 3 +++
 1 file changed, 3 insertions(+)

Comments

Gao Xiang June 28, 2024, 7:22 a.m. UTC | #1 
On 2024/6/28 14:29, libaokun@huaweicloud.com wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> When queuing ondemand_object_worker() to re-open the object,
> cachefiles_object is not pinned. The cachefiles_object may be freed when
> the pending read request is completed intentionally and the related
> erofs is umounted. If ondemand_object_worker() runs after the object is
> freed, it will incur use-after-free problem as shown below.
> 
> process A  processs B  process C  process D
> 
> cachefiles_ondemand_send_req()
> // send a read req X
> // wait for its completion
> 
>             // close ondemand fd
>             cachefiles_ondemand_fd_release()
>             // set object as CLOSE
> 
>                         cachefiles_ondemand_daemon_read()
>                         // set object as REOPENING
>                         queue_work(fscache_wq, &info->ondemand_work)
> 
>                                  // close /dev/cachefiles
>                                  cachefiles_daemon_release
>                                  cachefiles_flush_reqs
>                                  complete(&req->done)
> 
> // read req X is completed
> // umount the erofs fs
> cachefiles_put_object()
> // object will be freed
> cachefiles_ondemand_deinit_obj_info()
> kmem_cache_free(object)
>                         // both info and object are freed
>                         ondemand_object_worker()
> 
> When dropping an object, it is no longer necessary to reopen the object,
> so use cancel_work_sync() to cancel or wait for ondemand_object_worker()
> to finish.
> 
> Fixes: 0a7e54c1959c ("cachefiles: resend an open request if the read request's object is closed")
> Signed-off-by: Hou Tao <houtao1@huawei.com>
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> Reviewed-by: Jia Zhu <zhujia.zj@bytedance.com>
> Acked-by: Jeff Layton <jlayton@kernel.org>

Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Thanks,
Gao Xiang
diff mbox series

Patch

diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index 36b97ded16b4..1d5b970206d0 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -694,6 +694,9 @@  void cachefiles_ondemand_clean_object(struct cachefiles_object *object)
 		}
 	}
 	xa_unlock(&cache->reqs);
+
+	/* Wait for ondemand_object_worker() to finish to avoid UAF. */
+	cancel_work_sync(&object->ondemand->ondemand_work);
 }
 
 int cachefiles_ondemand_init_obj_info(struct cachefiles_object *object,