UBI: fix oops in error path

This patch fixes an oops in the error path of 'ubi_attach_mtd_dev()'. If
anything after 'uif_init()' fails, we get an oops in 'cancel_pending()'. The
reason is that 'uif_close()' drops the last reference count for 'ubi->dev' and
whole 'struct ubi_device' is freed. And then
'ubi_wl_close()'->'cancel_pending()' tries to access the 'ubi' pointer and
problems begin.

Note, in 'ubi_detach_mtd_dev()' function we get a device reference to
work-around this issue. Do the same in the error path of
'ubi_attach_mtd_dev()'.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 6d0d48395d8c..6c3fb5ab20f5 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -1019,6 +1019,8 @@ int ubi_attach_mtd_dev(struct mtd_info *mtd, int ubi_num, int vid_hdr_offset)
 out_debugfs:
         ubi_debugfs_exit_dev(ubi);
 out_uif:
+        get_device(&ubi->dev);
+        ubi_assert(ref);
         uif_close(ubi);
 out_detach:
         ubi_wl_close(ubi);