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Subject[PATCH v3] mtd: Fix gluebi NULL pointer dereference caused by ftl notifier
Date
If both flt.ko and gluebi.ko are loaded, the notiier 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],

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 mtdblock devices.

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/441107100.23734.1697904580252.JavaMail.zimbra@nod.at/ [2]
Signed-off-by: ZhaoLong Wang <wangzhaolong1@huawei.com>
---
drivers/mtd/mtd_blkdevs.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/mtd_blkdevs.c b/drivers/mtd/mtd_blkdevs.c
index ff18636e0889..5bc32108ca03 100644
--- a/drivers/mtd/mtd_blkdevs.c
+++ b/drivers/mtd/mtd_blkdevs.c
@@ -463,7 +463,7 @@ static void blktrans_notify_add(struct mtd_info *mtd)
{
struct mtd_blktrans_ops *tr;

- if (mtd->type == MTD_ABSENT)
+ if (mtd->type == MTD_ABSENT || mtd->type == MTD_UBIVOLUME)
return;

list_for_each_entry(tr, &blktrans_majors, list)
@@ -503,7 +503,7 @@ int register_mtd_blktrans(struct mtd_blktrans_ops *tr)
mutex_lock(&mtd_table_mutex);
list_add(&tr->list, &blktrans_majors);
mtd_for_each_device(mtd)
- if (mtd->type != MTD_ABSENT)
+ if (mtd->type != MTD_ABSENT && mtd->type != MTD_UBIVOLUME)
tr->add_mtd(tr, mtd);
mutex_unlock(&mtd_table_mutex);
return 0;
--
2.31.1
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