[PATCH 4/8] raid5-cache: fix a user-after-free bug
From: Shaohua Li <hidden>
Date: 2015-09-02 20:49:47
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
r5l_compress_stripe_end_list() can free an io_unit. This breaks the assumption only reclaimer can free io_unit. We can add a reference count based io_unit free, but since only reclaim can wait io_unit becoming to STRIPE_END state, we use a simple global wait queue here. Signed-off-by: Shaohua Li <redacted> --- drivers/md/raid5-cache.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 86b836c..2f5e2b8 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c@@ -78,6 +78,7 @@ struct r5l_log { * which are in IO_UNIT_STRIPE_END state (eg, * reclaim dones't wait for specific io_unit * switching to IO_UNIT_STRIPE_END state) */ + wait_queue_head_t iounit_wait; struct list_head no_space_stripes; /* pending stripes, log has no space */ spinlock_t no_space_stripes_lock;
@@ -108,7 +109,6 @@ struct r5l_io_unit { struct list_head stripe_list; /* stripes added to the io_unit */ int state; - wait_queue_head_t wait_state; }; /* r5l_io_unit state */
@@ -161,7 +161,6 @@ static struct r5l_io_unit *r5l_alloc_io_unit(struct r5l_log *log) INIT_LIST_HEAD(&io->log_sibling); INIT_LIST_HEAD(&io->stripe_list); io->state = IO_UNIT_RUNNING; - init_waitqueue_head(&io->wait_state); return io; }
@@ -242,8 +241,8 @@ static void __r5l_set_io_unit_state(struct r5l_io_unit *io, r5l_wake_reclaim(log, 0); r5l_compress_stripe_end_list(log); + wake_up(&log->iounit_wait); } - wake_up(&io->wait_state); } static void r5l_set_io_unit_state(struct r5l_io_unit *io,
@@ -617,10 +616,11 @@ void r5l_flush_stripe_to_raid(struct r5l_log *log) submit_bio(WRITE_FLUSH, &log->flush_bio); } -static void r5l_kick_io_unit(struct r5l_log *log, struct r5l_io_unit *io) +static void r5l_kick_io_unit(struct r5l_log *log) { md_wakeup_thread(log->rdev->mddev->thread); - wait_event(io->wait_state, io->state >= IO_UNIT_STRIPE_END); + wait_event_lock_irq(log->iounit_wait, !list_empty(&log->stripe_end_ios), + log->io_list_lock); } static void r5l_write_super(struct r5l_log *log, sector_t cp);
@@ -665,12 +665,7 @@ static void r5l_do_reclaim(struct r5l_log *log) else if (!list_empty(&log->running_ios)) target_list = &log->running_ios; - io = list_first_entry(target_list, - struct r5l_io_unit, log_sibling); - spin_unlock_irq(&log->io_list_lock); - /* nobody else can delete the io, we are safe */ - r5l_kick_io_unit(log, io); - spin_lock_irq(&log->io_list_lock); + r5l_kick_io_unit(log); } spin_unlock_irq(&log->io_list_lock);
@@ -1071,6 +1066,7 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev) log->rdev->mddev, "reclaim"); if (!log->reclaim_thread) goto reclaim_thread; + init_waitqueue_head(&log->iounit_wait); INIT_LIST_HEAD(&log->no_space_stripes); spin_lock_init(&log->no_space_stripes_lock);
--
1.8.1