diff options
| author | Lin Feng <linf@wangsu.com> | 2021-11-12 13:36:29 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2021-12-14 20:32:54 -0700 |
| commit | aa97f6cdb7e92909e17c8ca63e622fcb81d57a57 (patch) | |
| tree | 3fe44f476f63dfe49cf447a31d3a5388a0267cf6 | |
| parent | cb2ac2912a9ca7d3d26291c511939a41361d2d83 (diff) | |
bcache: fix NULL pointer reference in cached_dev_detach_finish
Commit 0259d4498ba4 ("bcache: move calc_cached_dev_sectors to proper
place on backing device detach") tries to fix calc_cached_dev_sectors
when bcache device detaches, but now we have:
cached_dev_detach_finish
...
bcache_device_detach(&dc->disk);
...
closure_put(&d->c->caching);
d->c = NULL; [*explicitly set dc->disk.c to NULL*]
list_move(&dc->list, &uncached_devices);
calc_cached_dev_sectors(dc->disk.c); [*passing a NULL pointer*]
...
Upper codeflows shows how bug happens, this patch fix the problem by
caching dc->disk.c beforehand, and cache_set won't be freed under us
because c->caching closure at least holds a reference count and closure
callback __cache_set_unregister only being called by bch_cache_set_stop
which using closure_queue(&c->caching), that means c->caching closure
callback for destroying cache_set won't be trigger by previous
closure_put(&d->c->caching).
So at this stage(while cached_dev_detach_finish is calling) it's safe to
access cache_set dc->disk.c.
Fixes: 0259d4498ba4 ("bcache: move calc_cached_dev_sectors to proper place on backing device detach")
Signed-off-by: Lin Feng <linf@wangsu.com>
Signed-off-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20211112053629.3437-2-colyli@suse.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/md/bcache/super.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 86b9e355c583..140f35dc0c45 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -1139,6 +1139,7 @@ static void cancel_writeback_rate_update_dwork(struct cached_dev *dc) static void cached_dev_detach_finish(struct work_struct *w) { struct cached_dev *dc = container_of(w, struct cached_dev, detach); + struct cache_set *c = dc->disk.c; BUG_ON(!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)); BUG_ON(refcount_read(&dc->count)); @@ -1156,7 +1157,7 @@ static void cached_dev_detach_finish(struct work_struct *w) bcache_device_detach(&dc->disk); list_move(&dc->list, &uncached_devices); - calc_cached_dev_sectors(dc->disk.c); + calc_cached_dev_sectors(c); clear_bit(BCACHE_DEV_DETACHING, &dc->disk.flags); clear_bit(BCACHE_DEV_UNLINK_DONE, &dc->disk.flags); |