[ Upstream commit a43bdc376deab5fff1ceb93dca55bcab8dbdc1d6 ] If both ftl.ko and gluebi.ko are loaded, the notifier of ftl triggers NULL pointer dereference when trying to access ‘gluebi->desc’ in gluebi_read(). ubi_gluebi_init ubi_register_volume_notifier ubi_enumerate_volumes ubi_notify_all gluebi_notify nb->notifier_call() gluebi_create mtd_device_register mtd_device_parse_register add_mtd_device blktrans_notify_add not->add() ftl_add_mtd tr->add_mtd() scan_header mtd_read mtd_read_oob mtd_read_oob_std gluebi_read mtd->read() gluebi->desc - NULL Detailed reproduction information available at the Link [1], In the normal case, obtain gluebi->desc in the gluebi_get_device(), and access gluebi->desc in the gluebi_read(). However, gluebi_get_device() is not executed in advance in the ftl_add_mtd() process, which leads to NULL pointer dereference. The solution for the gluebi module is to run jffs2 on the UBI volume without considering working with ftl or mtdblock [2]. Therefore, this problem can be avoided by preventing gluebi from creating the mtdblock device after creating mtd partition of the type MTD_UBIVOLUME. Fixes: 2ba3d76a1e29 ("UBI: make gluebi a separate module") Link: https://bugzilla.kernel.org/show_bug.cgi?id=217992 [1] Link: https://lore.kernel.org/lkml/[email protected]/ [2] Signed-off-by: ZhaoLong Wang <[email protected]> Reviewed-by: Zhihao Cheng <[email protected]> Acked-by: Richard Weinberger <[email protected]> Signed-off-by: Miquel Raynal <[email protected]> Link: https://lore.kernel.org/linux-mtd/[email protected] Signed-off-by: Sasha Levin <[email protected]>