[PATCH AUTOSEL 5.6 19/68] null_blk: Handle null_add_dev() failures properly

Sasha Levin
2020-04-10T04:02:43Z

From: Bart Van Assche <bvanassche@acm.org>

[ Upstream commit 9b03b713082a31a5b90e0a893c72aa620e255c26 ]

If null_add_dev() fails then null_del_dev() is called with a NULL argument.
Make null_del_dev() handle this scenario correctly. This patch fixes the
following KASAN complaint:

null-ptr-deref in null_del_dev+0x28/0x280 [null_blk]
Read of size 8 at addr 0000000000000000 by task find/1062

Call Trace:
dump_stack+0xa5/0xe6
__kasan_report.cold+0x65/0x99
kasan_report+0x16/0x20
__asan_load8+0x58/0x90
null_del_dev+0x28/0x280 [null_blk]
nullb_group_drop_item+0x7e/0xa0 [null_blk]
client_drop_item+0x53/0x80 [configfs]
configfs_rmdir+0x395/0x4e0 [configfs]
vfs_rmdir+0xb6/0x220
do_rmdir+0x238/0x2c0
__x64_sys_unlinkat+0x75/0x90
do_syscall_64+0x6f/0x2f0
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Cc: Johannes Thumshirn <jth@kernel.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/block/null_blk_main.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 8ada43b3eca13..d5b4a92033d48 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -1432,7 +1432,12 @@ static void cleanup_queues(struct nullb *nullb)

static void null_del_dev(struct nullb *nullb)
{
- struct nullb_device *dev = nullb->dev;
+ struct nullb_device *dev;
+
+ if (!nullb)
+ return;
+
+ dev = nullb->dev;

ida_simple_remove(&nullb_indexes, nullb->index);

--
2.20.1