From e9c80881b383df54cd519e10314dce4c47df8b8a Mon Sep 17 00:00:00 2001 From: Coly Li Date: Fri, 13 Oct 2017 16:35:29 -0700 Subject: [PATCH] bcache: check ca->alloc_thread initialized before wake up it commit 91af8300d9c1d7c6b6a2fd754109e08d4798b8d8 upstream. In bcache code, sysfs entries are created before all resources get allocated, e.g. allocation thread of a cache set. There is posibility for NULL pointer deference if a resource is accessed but which is not initialized yet. Indeed Jorg Bornschein catches one on cache set allocation thread and gets a kernel oops. The reason for this bug is, when bch_bucket_alloc() is called during cache set registration and attaching, ca->alloc_thread is not properly allocated and initialized yet, call wake_up_process() on ca->alloc_thread triggers NULL pointer deference failure. A simple and fast fix is, before waking up ca->alloc_thread, checking whether it is allocated, and only wake up ca->alloc_thread when it is not NULL. Signed-off-by: Coly Li Reported-by: Jorg Bornschein Cc: Kent Overstreet Reviewed-by: Michael Lyle Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- drivers/md/bcache/alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c index 08035634795c..c9934139d609 100644 --- a/drivers/md/bcache/alloc.c +++ b/drivers/md/bcache/alloc.c @@ -407,7 +407,8 @@ long bch_bucket_alloc(struct cache *ca, unsigned reserve, bool wait) finish_wait(&ca->set->bucket_wait, &w); out: - wake_up_process(ca->alloc_thread); + if (ca->alloc_thread) + wake_up_process(ca->alloc_thread); trace_bcache_alloc(ca, reserve); -- 2.20.1