From 45222b9a9016488289a1938a528239c3b83eddb1 Mon Sep 17 00:00:00 2001 From: Alexander Bulekov Date: Thu, 18 Jun 2020 12:05:16 -0400 Subject: [PATCH] fuzz: fix broken qtest check at rcu_disable_atfork The qtest_enabled check introduced in d6919e4 always returns false, as it is called prior to configure_accelerators(). Instead of trying to skip rcu_disable_atfork in qemu_main, simply call rcu_enable_atfork in the fuzzer, after qemu_main returns. Reported-by: Thomas Huth Signed-off-by: Alexander Bulekov Message-Id: <20200618160516.2817-1-alxndr@bu.edu> Signed-off-by: Thomas Huth --- softmmu/vl.c | 12 +----------- tests/qtest/fuzz/fuzz.c | 3 +++ 2 files changed, 4 insertions(+), 11 deletions(-) diff --git a/softmmu/vl.c b/softmmu/vl.c index 3e15ee2435..9da2e23144 100644 --- a/softmmu/vl.c +++ b/softmmu/vl.c @@ -3832,17 +3832,7 @@ void qemu_init(int argc, char **argv, char **envp) machine_class); os_daemonize(); - - /* - * If QTest is enabled, keep the rcu_atfork enabled, since system processes - * may be forked testing purposes (e.g. fork-server based fuzzing) The fork - * should happen before a signle cpu instruction is executed, to prevent - * deadlocks. See commit 73c6e40, rcu: "completely disable pthread_atfork - * callbacks as soon as possible" - */ - if (!qtest_enabled()) { - rcu_disable_atfork(); - } + rcu_disable_atfork(); if (pid_file && !qemu_write_pidfile(pid_file, &err)) { error_reportf_err(err, "cannot create PID file: "); diff --git a/tests/qtest/fuzz/fuzz.c b/tests/qtest/fuzz/fuzz.c index a44fe479db..a36d9038e0 100644 --- a/tests/qtest/fuzz/fuzz.c +++ b/tests/qtest/fuzz/fuzz.c @@ -211,5 +211,8 @@ int LLVMFuzzerInitialize(int *argc, char ***argv, char ***envp) qemu_init(result.we_wordc, result.we_wordv, NULL); + /* re-enable the rcu atfork, which was previously disabled in qemu_init */ + rcu_enable_atfork(); + return 0; }