6.9-stable review patch. If anyone has any objections, please let me know.
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From: Baokun Li libaokun1@huawei.com
[ Upstream commit 0fc75c5940fa634d84e64c93bfc388e1274ed013 ]
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@huawei.com Link: https://lore.kernel.org/r/20240522114308.2402121-3-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 Reviewed-by: Jingbo Xu jefflexu@linux.alibaba.com Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/cachefiles/daemon.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/fs/cachefiles/daemon.c b/fs/cachefiles/daemon.c index 6465e25742309..ccb7b707ea4b7 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);