2021-06-12 14:39:03

by Pavel Skripkin

Subject: [PATCH] nilfs2: fix memory leak in nilfs_sysfs_delete_device_group

My local syzbot instance hit memory leak in nilfs2.
The problem was in missing kobject_put() in
nilfs_sysfs_delete_device_group().

kobject_del() does not call kobject_cleanup() for
passed kobject and it leads to leaking duped
kobject name if kobject_put() was not called.

Fail log:

BUG: memory leak
unreferenced object 0xffff8880596171e0 (size 8):
comm "syz-executor379", pid 8381, jiffies 4294980258 (age 21.100s)
hex dump (first 8 bytes):
6c 6f 6f 70 30 00 00 00 loop0...
backtrace:
[<ffffffff81a2c656>] kstrdup+0x36/0x70 mm/util.c:60
[<ffffffff81a2c6e3>] kstrdup_const+0x53/0x80 mm/util.c:83
[<ffffffff83ccc698>] kvasprintf_const+0x108/0x190 lib/kasprintf.c:48
[<ffffffff83e99926>] kobject_set_name_vargs+0x56/0x150 lib/kobject.c:289
[<ffffffff83e99fd9>] kobject_add_varg lib/kobject.c:384 [inline]
[<ffffffff83e99fd9>] kobject_init_and_add+0xc9/0x160 lib/kobject.c:473
[<ffffffff8304e840>] nilfs_sysfs_create_device_group+0x150/0x800 fs/nilfs2/sysfs.c:999
[<ffffffff830159f6>] init_nilfs+0xe26/0x12b0 fs/nilfs2/the_nilfs.c:637

Fixes: da7141fb78db ("nilfs2: add /sys/fs/nilfs2/<device> group")
Signed-off-by: Pavel Skripkin <[email protected]>
---
fs/nilfs2/sysfs.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 303d71430bdd..9c6c0e2e5880 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -1053,6 +1053,7 @@ void nilfs_sysfs_delete_device_group(struct the_nilfs *nilfs)
nilfs_sysfs_delete_superblock_group(nilfs);
nilfs_sysfs_delete_segctor_group(nilfs);
kobject_del(&nilfs->ns_dev_kobj);
+ kobject_put(&nilfs->ns_dev_kobj);
kfree(nilfs->ns_dev_subgroups);
}

--
2.32.0

2021-06-24 19:31:09

by Ryusuke Konishi

Subject: Re: [PATCH] nilfs2: fix memory leak in nilfs_sysfs_delete_device_group

Hi Andrew,

On Sat, Jun 12, 2021 at 11:06 PM Pavel Skripkin <[email protected]> wrote:
>
> My local syzbot instance hit memory leak in nilfs2.
> The problem was in missing kobject_put() in
> nilfs_sysfs_delete_device_group().
>
> kobject_del() does not call kobject_cleanup() for
> passed kobject and it leads to leaking duped
> kobject name if kobject_put() was not called.
>
> Fail log:
>
> BUG: memory leak
> unreferenced object 0xffff8880596171e0 (size 8):
> comm "syz-executor379", pid 8381, jiffies 4294980258 (age 21.100s)
> hex dump (first 8 bytes):
> 6c 6f 6f 70 30 00 00 00 loop0...
> backtrace:
> [<ffffffff81a2c656>] kstrdup+0x36/0x70 mm/util.c:60
> [<ffffffff81a2c6e3>] kstrdup_const+0x53/0x80 mm/util.c:83
> [<ffffffff83ccc698>] kvasprintf_const+0x108/0x190 lib/kasprintf.c:48
> [<ffffffff83e99926>] kobject_set_name_vargs+0x56/0x150 lib/kobject.c:289
> [<ffffffff83e99fd9>] kobject_add_varg lib/kobject.c:384 [inline]
> [<ffffffff83e99fd9>] kobject_init_and_add+0xc9/0x160 lib/kobject.c:473
> [<ffffffff8304e840>] nilfs_sysfs_create_device_group+0x150/0x800 fs/nilfs2/sysfs.c:999
> [<ffffffff830159f6>] init_nilfs+0xe26/0x12b0 fs/nilfs2/the_nilfs.c:637
>
> Fixes: da7141fb78db ("nilfs2: add /sys/fs/nilfs2/<device> group")
> Signed-off-by: Pavel Skripkin <[email protected]>

This fix looks correct to me.

Acked-by: Ryusuke Konishi <[email protected]>

Thanks,
Ryusuke Konishi

> ---
> fs/nilfs2/sysfs.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
> index 303d71430bdd..9c6c0e2e5880 100644
> --- a/fs/nilfs2/sysfs.c
> +++ b/fs/nilfs2/sysfs.c
> @@ -1053,6 +1053,7 @@ void nilfs_sysfs_delete_device_group(struct the_nilfs *nilfs)
> nilfs_sysfs_delete_superblock_group(nilfs);
> nilfs_sysfs_delete_segctor_group(nilfs);
> kobject_del(&nilfs->ns_dev_kobj);
> + kobject_put(&nilfs->ns_dev_kobj);
> kfree(nilfs->ns_dev_subgroups);
> }
>
> --
> 2.32.0
>