From 589a594be1fb8815b3f18e517be696c48664f728 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 9 Dec 2010 17:02:14 +1100 Subject: [PATCH] md: protect against NULL reference when waiting to start a raid10. When we fail to start a raid10 for some reason, we call md_unregister_thread to kill the thread that was created. Unfortunately md_thread() will then make one call into the handler (raid10d) even though md_wakeup_thread has not been called. This is not safe and as md_unregister_thread is called after mddev->private has been set to NULL, it will definitely cause a NULL dereference. So fix this at both ends: - md_thread should only call the handler if THREAD_WAKEUP has been set. - raid10 should call md_unregister_thread before setting things to NULL just like all the other raid modules do. This is applicable to 2.6.35 and later. Cc: stable@kernel.org Reported-by: "Citizen" Signed-off-by: NeilBrown --- drivers/md/md.c | 5 ++--- drivers/md/raid10.c | 2 +- 2 files changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index b757da175180..e71c5fa527f5 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -6044,9 +6044,8 @@ static int md_thread(void * arg) || kthread_should_stop(), thread->timeout); - clear_bit(THREAD_WAKEUP, &thread->flags); - - thread->run(thread->mddev); + if (test_and_clear_bit(THREAD_WAKEUP, &thread->flags)) + thread->run(thread->mddev); } return 0; diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index c67aa54694ae..0641674827f0 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -2397,13 +2397,13 @@ static int run(mddev_t *mddev) return 0; out_free_conf: + md_unregister_thread(mddev->thread); if (conf->r10bio_pool) mempool_destroy(conf->r10bio_pool); safe_put_page(conf->tmppage); kfree(conf->mirrors); kfree(conf); mddev->private = NULL; - md_unregister_thread(mddev->thread); out: return -EIO; }