Re: [PATCH] configfs: Fix possible use-after-free in configfs_register_group

[YueHaibing]

Friendly ping...

On 2019/4/16 14:44, Yue Haibing wrote:
> From: YueHaibing <yuehaibing@xxxxxxxxxx>
> 
> Syzkaller report this:
> 
> BUG: KASAN: use-after-free in __list_add_valid+0xd4/0xe0 lib/list_debug.c:26
> Read of size 8 at addr ffff8881ef61ae20 by task syz-executor.0/5996
> 
> CPU: 1 PID: 5996 Comm: syz-executor.0 Tainted: G         C        5.0.0+ #5
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0xa9/0x10e lib/dump_stack.c:113
>  print_address_description+0x65/0x270 mm/kasan/report.c:187
>  kasan_report+0x149/0x18d mm/kasan/report.c:317
>  __list_add_valid+0xd4/0xe0 lib/list_debug.c:26
>  __list_add include/linux/list.h:60 [inline]
>  list_add_tail include/linux/list.h:93 [inline]
>  link_obj+0xb0/0x190 fs/configfs/dir.c:759
>  link_group+0x1c/0x130 fs/configfs/dir.c:784
>  configfs_register_group+0x56/0x1e0 fs/configfs/dir.c:1751
>  configfs_register_default_group+0x72/0xc0 fs/configfs/dir.c:1834
>  ? 0xffffffffc1be0000
>  iio_sw_trigger_init+0x23/0x1000 [industrialio_sw_trigger]
>  do_one_initcall+0xbc/0x47d init/main.c:887
>  do_init_module+0x1b5/0x547 kernel/module.c:3456
>  load_module+0x6405/0x8c10 kernel/module.c:3804
>  __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
>  do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x462e99
> Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f494ecbcc58 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
> RAX: ffffffffffffffda RBX: 000000000073bf00 RCX: 0000000000462e99
> RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000003
> RBP: 00007f494ecbcc70 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f494ecbd6bc
> R13: 00000000004bcefa R14: 00000000006f6fb0 R15: 0000000000000004
> 
> Allocated by task 5987:
>  set_track mm/kasan/common.c:87 [inline]
>  __kasan_kmalloc.constprop.3+0xa0/0xd0 mm/kasan/common.c:497
>  kmalloc include/linux/slab.h:545 [inline]
>  kzalloc include/linux/slab.h:740 [inline]
>  configfs_register_default_group+0x4c/0xc0 fs/configfs/dir.c:1829
>  0xffffffffc1bd0023
>  do_one_initcall+0xbc/0x47d init/main.c:887
>  do_init_module+0x1b5/0x547 kernel/module.c:3456
>  load_module+0x6405/0x8c10 kernel/module.c:3804
>  __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
>  do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 5987:
>  set_track mm/kasan/common.c:87 [inline]
>  __kasan_slab_free+0x130/0x180 mm/kasan/common.c:459
>  slab_free_hook mm/slub.c:1429 [inline]
>  slab_free_freelist_hook mm/slub.c:1456 [inline]
>  slab_free mm/slub.c:3003 [inline]
>  kfree+0xe1/0x270 mm/slub.c:3955
>  configfs_register_default_group+0x9a/0xc0 fs/configfs/dir.c:1836
>  0xffffffffc1bd0023
>  do_one_initcall+0xbc/0x47d init/main.c:887
>  do_init_module+0x1b5/0x547 kernel/module.c:3456
>  load_module+0x6405/0x8c10 kernel/module.c:3804
>  __do_sys_finit_module+0x162/0x190 kernel/module.c:3898
>  do_syscall_64+0x9f/0x450 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> The buggy address belongs to the object at ffff8881ef61ae00
>  which belongs to the cache kmalloc-192 of size 192
> The buggy address is located 32 bytes inside of
>  192-byte region [ffff8881ef61ae00, ffff8881ef61aec0)
> The buggy address belongs to the page:
> page:ffffea0007bd8680 count:1 mapcount:0 mapping:ffff8881f6c03000 index:0xffff8881ef61a700
> flags: 0x2fffc0000000200(slab)
> raw: 02fffc0000000200 ffffea0007ca4740 0000000500000005 ffff8881f6c03000
> raw: ffff8881ef61a700 000000008010000c 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff8881ef61ad00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffff8881ef61ad80: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>> ffff8881ef61ae00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                ^
>  ffff8881ef61ae80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>  ffff8881ef61af00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> 
> In configfs_register_group(), if create_default_group() failed, we
> forgot to unlink group. It will left a invalid item in parent list,
> which may trigger a use-after-free issue.
> 
> Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> Fixes: 5cf6a51e6062 ("configfs: allow dynamic group creation")
> Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
> ---
>  fs/configfs/dir.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
> index 591e82b..5e7932d 100644
> --- a/fs/configfs/dir.c
> +++ b/fs/configfs/dir.c
> @@ -1757,12 +1757,19 @@ int configfs_register_group(struct config_group *parent_group,
>  
>  	inode_lock_nested(d_inode(parent), I_MUTEX_PARENT);
>  	ret = create_default_group(parent_group, group);
> -	if (!ret) {
> -		spin_lock(&configfs_dirent_lock);
> -		configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
> -		spin_unlock(&configfs_dirent_lock);
> -	}
> +	if (ret)
> +		goto err_out;
> +
> +	spin_lock(&configfs_dirent_lock);
> +	configfs_dir_set_ready(group->cg_item.ci_dentry->d_fsdata);
> +	spin_unlock(&configfs_dirent_lock);
> +	inode_unlock(d_inode(parent));
> +	return 0;
> +err_out:
>  	inode_unlock(d_inode(parent));
> +	mutex_lock(&subsys->su_mutex);
> +	unlink_group(group);
> +	mutex_unlock(&subsys->su_mutex);
>  	return ret;
>  }
>  EXPORT_SYMBOL(configfs_register_group);
>