On 2024/5/20 10:20, Gao Xiang wrote:
On 2024/5/15 16:45, libaokun@xxxxxxxxxxxxxxx wrote:
From: Baokun Li <libaokun1@xxxxxxxxxx>
The subject line can be
"cachefiles: remove requests from xarray during flushing requests"
Thank you very much for the correction! I will update my patch.
Even with CACHEFILES_DEAD set, we can still read the requests, so in the
following concurrency the request may be used after it has been freed:
mount | daemon_thread1 | daemon_thread2
------------------------------------------------------------
cachefiles_ondemand_init_object
cachefiles_ondemand_send_req
REQ_A = kzalloc(sizeof(*req) + data_len)
wait_for_completion(&REQ_A->done)
cachefiles_daemon_read
cachefiles_ondemand_daemon_read
// close dev fd
cachefiles_flush_reqs
complete(&REQ_A->done)
kfree(REQ_A)
xa_lock(&cache->reqs);
cachefiles_ondemand_select_req
req->msg.opcode != CACHEFILES_OP_READ
// req use-after-free !!!
xa_unlock(&cache->reqs);
xa_destroy(&cache->reqs)
Hence remove requests from cache->reqs when flushing them to avoid
accessing freed requests.
Fixes: c8383054506c ("cachefiles: notify the user daemon when looking
up cookie")
Signed-off-by: Baokun Li <libaokun1@xxxxxxxxxx>
Reviewed-by: Jia Zhu <zhujia.zj@xxxxxxxxxxxxx>
Reviewed-by: Gao Xiang <hsiangkao@xxxxxxxxxxxxxxxxx>
Thanks,
Gao Xiang
Thanks a lot for the review!
Cheers,
Baokun
---
fs/cachefiles/daemon.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c
index 6465e2574230..ccb7b707ea4b 100644
--- a/fs/cachefiles/daemon.c
+++ b/fs/cachefiles/daemon.c
@@ -159,6 +159,7 @@ static void cachefiles_flush_reqs(struct
cachefiles_cache *cache)
xa_for_each(xa, index, req) {
req->error = -EIO;
complete(&req->done);
+ __xa_erase(xa, index);
}
xa_unlock(xa);
--
With Best Regards,
Baokun Li
