2022-10-29 07:49:10

by Chen Zhongjin

Subject: [PATCH] block: Fix possible memory leak for rq_wb on add_disk failure

kmemleak reported memory leaks in device_add_disk():

kmemleak: 3 new suspected memory leaks

unreferenced object 0xffff88800f420800 (size 512):
comm "modprobe", pid 4275, jiffies 4295639067 (age 223.512s)
hex dump (first 32 bytes):
04 00 00 00 08 00 00 00 01 00 00 00 00 00 00 00 ................
00 e1 f5 05 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
[<00000000d3662699>] kmalloc_trace+0x26/0x60
[<00000000edc7aadc>] wbt_init+0x50/0x6f0
[<0000000069601d16>] wbt_enable_default+0x157/0x1c0
[<0000000028fc393f>] blk_register_queue+0x2a4/0x420
[<000000007345a042>] device_add_disk+0x6fd/0xe40
[<0000000060e6aab0>] nbd_dev_add+0x828/0xbf0 [nbd]
...

It is because the memory allocated in wbt_enable_default() is not
released in device_add_disk() error path.
Normally, these memory are freed in:

del_gendisk()
rq_qos_exit()
rqos->ops->exit(rqos);
wbt_exit()

So rq_qos_exit() is called to free the rq_wb memory for wbt_init().
However in the error path of device_add_disk(), only
blk_unregister_queue() is called and make rq_wb memory leaked.

Add rq_qos_exit() to the error path to fix it.

Fixes: 83cbce957446 ("block: add error handling for device_add_disk / add_disk")
Signed-off-by: Chen Zhongjin <[email protected]>
---
block/genhd.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/block/genhd.c b/block/genhd.c
index fee90eb98b4a..0f9769db2de8 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -527,6 +527,7 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
bdi_unregister(disk->bdi);
out_unregister_queue:
blk_unregister_queue(disk);
+ rq_qos_exit(disk->queue);
out_put_slave_dir:
kobject_put(disk->slave_dir);
out_put_holder_dir:
--
2.17.1

2022-10-30 09:44:45

by Christoph Hellwig

Subject: Re: [PATCH] block: Fix possible memory leak for rq_wb on add_disk failure

Looks good:

Reviewed-by: Christoph Hellwig <[email protected]>

2022-10-31 14:16:34

by Jens Axboe

Subject: Re: [PATCH] block: Fix possible memory leak for rq_wb on add_disk failure

On Sat, 29 Oct 2022 15:13:55 +0800, Chen Zhongjin wrote:
> kmemleak reported memory leaks in device_add_disk():
>
> kmemleak: 3 new suspected memory leaks
>
> unreferenced object 0xffff88800f420800 (size 512):
> comm "modprobe", pid 4275, jiffies 4295639067 (age 223.512s)
> hex dump (first 32 bytes):
> 04 00 00 00 08 00 00 00 01 00 00 00 00 00 00 00 ................
> 00 e1 f5 05 00 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<00000000d3662699>] kmalloc_trace+0x26/0x60
> [<00000000edc7aadc>] wbt_init+0x50/0x6f0
> [<0000000069601d16>] wbt_enable_default+0x157/0x1c0
> [<0000000028fc393f>] blk_register_queue+0x2a4/0x420
> [<000000007345a042>] device_add_disk+0x6fd/0xe40
> [<0000000060e6aab0>] nbd_dev_add+0x828/0xbf0 [nbd]
> ...
>
> [...]

Applied, thanks!

[1/1] block: Fix possible memory leak for rq_wb on add_disk failure
(no commit info)

Best regards,
--
Jens Axboe