lkml.org 
[lkml]   [2023]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] ext4: fix task hung in ext4_xattr_delete_inode
From
On 2023/1/10 19:34, Jan Kara wrote:
> On Tue 10-01-23 12:27:09, Baokun Li wrote:
>> Syzbot reported a hung task problem:
>> ==================================================================
>> INFO: task syz-executor232:5073 blocked for more than 143 seconds.
>> Not tainted 6.2.0-rc2-syzkaller-00024-g512dee0c00ad #0
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> task:syz-exec232 state:D stack:21024 pid:5073 ppid:5072 flags:0x00004004
>> Call Trace:
>> <TASK>
>> context_switch kernel/sched/core.c:5244 [inline]
>> __schedule+0x995/0xe20 kernel/sched/core.c:6555
>> schedule+0xcb/0x190 kernel/sched/core.c:6631
>> __wait_on_freeing_inode fs/inode.c:2196 [inline]
>> find_inode_fast+0x35a/0x4c0 fs/inode.c:950
>> iget_locked+0xb1/0x830 fs/inode.c:1273
>> __ext4_iget+0x22e/0x3ed0 fs/ext4/inode.c:4861
>> ext4_xattr_inode_iget+0x68/0x4e0 fs/ext4/xattr.c:389
>> ext4_xattr_inode_dec_ref_all+0x1a7/0xe50 fs/ext4/xattr.c:1148
>> ext4_xattr_delete_inode+0xb04/0xcd0 fs/ext4/xattr.c:2880
>> ext4_evict_inode+0xd7c/0x10b0 fs/ext4/inode.c:296
>> evict+0x2a4/0x620 fs/inode.c:664
>> ext4_orphan_cleanup+0xb60/0x1340 fs/ext4/orphan.c:474
>> __ext4_fill_super fs/ext4/super.c:5516 [inline]
>> ext4_fill_super+0x81cd/0x8700 fs/ext4/super.c:5644
>> get_tree_bdev+0x400/0x620 fs/super.c:1282
>> vfs_get_tree+0x88/0x270 fs/super.c:1489
>> do_new_mount+0x289/0xad0 fs/namespace.c:3145
>> do_mount fs/namespace.c:3488 [inline]
>> __do_sys_mount fs/namespace.c:3697 [inline]
>> __se_sys_mount+0x2d3/0x3c0 fs/namespace.c:3674
>> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>> do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
>> entry_SYSCALL_64_after_hwframe+0x63/0xcd
>> RIP: 0033:0x7fa5406fd5ea
>> RSP: 002b:00007ffc7232f968 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
>> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fa5406fd5ea
>> RDX: 0000000020000440 RSI: 0000000020000000 RDI: 00007ffc7232f970
>> RBP: 00007ffc7232f970 R08: 00007ffc7232f9b0 R09: 0000000000000432
>> R10: 0000000000804a03 R11: 0000000000000202 R12: 0000000000000004
>> R13: 0000555556a7a2c0 R14: 00007ffc7232f9b0 R15: 0000000000000000
>> </TASK>
>> ==================================================================
>>
>> The problem is that the inode contains an xattr entry with ea_inum of 15
>> when cleaning up an orphan inode <15>. When evict inode <15>, the reference
>> counting of the corresponding EA inode is decreased. When EA inode <15> is
>> found by find_inode_fast() in __ext4_iget(), it is found that the EA inode
>> holds the I_FREEING flag and waits for the EA inode to complete deletion.
>> As a result, when inode <15> is being deleted, we wait for inode <15> to
>> complete the deletion, resulting in an infinite loop and triggering Hung
>> Task. To solve this problem, we only need to check whether the ino of EA
>> inode and parent is the same before getting EA inode.
>>
>> Link: https://syzkaller.appspot.com/bug?extid=77d6fcc37bbb92f26048
>> Reported-by: syzbot+77d6fcc37bbb92f26048@syzkaller.appspotmail.com
>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
>> ---
>> fs/ext4/xattr.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
>> index 7decaaf27e82..9ff8fcf78bb8 100644
>> --- a/fs/ext4/xattr.c
>> +++ b/fs/ext4/xattr.c
>> @@ -386,6 +386,13 @@ static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino,
>> struct inode *inode;
>> int err;
>>
> Perhaps add a comment here like:
>
> /*
> * We have to check for this corruption early as otherwise
> * iget_locked() could wait indefinitely for the state of our
> * parent inode.
> */
Totally agree! Very accurate comment!
>> + if (parent->i_ino == ea_ino) {
>> + ext4_error(parent->i_sb,
>> + "Parent and EA inode have the same ino %lu", ea_ino);
>> + err = -EUCLEAN;
> ^^ I prefer -EFSCORRUPTED here. It is the same
> value but more descriptive name :).
OK! I will replace EUCLEAN with EFSCORRUPTED in v2.
>> + goto error;
> ^^ Just "return err" here. This will try to iput()
> uninitialized pointer.
>
> Honza
>
Indeed! I'm sorry I didn't notice this uninitialized variable.

Thank you very much for your review!
I will send a patch V2 with the changes suggested by you.
--
With Best Regards,
Baokun Li
.

\
 
 \ /
  Last update: 2023-03-26 23:34    [W:0.047 / U:0.036 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site