This is a note to let you know that I've just added the patch titled
bcache: check ca->alloc_thread initialized before wake up it
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: bcache-check-ca-alloc_thread-initialized-before-wake-up-it.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 91af8300d9c1d7c6b6a2fd754109e08d4798b8d8 Mon Sep 17 00:00:00 2001
From: Coly Li colyli@suse.de Date: Fri, 13 Oct 2017 16:35:29 -0700 Subject: bcache: check ca->alloc_thread initialized before wake up it
From: Coly Li colyli@suse.de
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 colyli@suse.de Reported-by: Jorg Bornschein jb@capsec.org Cc: Kent Overstreet kent.overstreet@gmail.com Reviewed-by: Michael Lyle mlyle@lyle.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/md/bcache/alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/md/bcache/alloc.c +++ b/drivers/md/bcache/alloc.c @@ -406,7 +406,8 @@ long bch_bucket_alloc(struct cache *ca,
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);
Patches currently in stable-queue which might be from colyli@suse.de are
queue-4.4/bcache-only-permit-to-recovery-read-error-when-cache-device-is-clean.patch queue-4.4/bcache-check-ca-alloc_thread-initialized-before-wake-up-it.patch