| 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); |
| |
