From: Baokun Li <libaokun1@huawei.com> mainline inclusion from mainline-v6.10-rc4 commit 0fc75c5940fa634d84e64c93bfc388e1274ed013 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IA6I1T Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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: Zizhi Wo <wozizhi@huawei.com> --- 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); -- 2.39.2