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authorColy Li <colyli@suse.de>2017-10-13 16:35:29 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-30 08:37:20 +0000
commit85c79043808d400ace74c99526fb9f4f67253102 (patch)
treece6aeef135ca5621662195b1b678cc6474aa6c2b /drivers/md
parent9c093a258350e86f781f23fbbef4e3d761c6b1e3 (diff)
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 <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>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/bcache/alloc.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index 8eeab72b93e2..ea47980949ef 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -406,7 +406,8 @@ 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);