6.9-stable review patch. If anyone has any objections, please let me know.
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From: Hou Tao houtao1@huawei.com
[ Upstream commit 12e009d60852f7bce0afc373ca0b320f14150418 ]
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 Link: https://lore.kernel.org/r/20240628062930.2467993-8-libaokun@huaweicloud.com Acked-by: Jeff Layton jlayton@kernel.org Reviewed-by: Jia Zhu zhujia.zj@bytedance.com Reviewed-by: Gao Xiang hsiangkao@linux.alibaba.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/cachefiles/ondemand.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c index 1c0fa7412a6fa..6b94f616e6579 100644 --- a/fs/cachefiles/ondemand.c +++ b/fs/cachefiles/ondemand.c @@ -661,6 +661,9 @@ 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,