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* [PATCH] ext4: fix null-ptr-deref in ext4_write_info
@ 2022-08-05 12:39 Baokun Li
  2022-08-05 13:07 ` Lukas Czerner
  2022-09-27 21:53 ` Theodore Ts'o
  0 siblings, 2 replies; 5+ messages in thread
From: Baokun Li @ 2022-08-05 12:39 UTC (permalink / raw)
  To: linux-ext4
  Cc: tytso, adilger.kernel, jack, ritesh.list, lczerner, enwlinux,
	linux-kernel, yi.zhang, yebin10, yukuai3, libaokun1

I caught a null-ptr-deref bug as follows:
==================================================================
KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
RIP: 0010:ext4_write_info+0x53/0x1b0
[...]
Call Trace:
 dquot_writeback_dquots+0x341/0x9a0
 ext4_sync_fs+0x19e/0x800
 __sync_filesystem+0x83/0x100
 sync_filesystem+0x89/0xf0
 generic_shutdown_super+0x79/0x3e0
 kill_block_super+0xa1/0x110
 deactivate_locked_super+0xac/0x130
 deactivate_super+0xb6/0xd0
 cleanup_mnt+0x289/0x400
 __cleanup_mnt+0x16/0x20
 task_work_run+0x11c/0x1c0
 exit_to_user_mode_prepare+0x203/0x210
 syscall_exit_to_user_mode+0x5b/0x3a0
 do_syscall_64+0x59/0x70
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
 ==================================================================

Above issue may happen as follows:
-------------------------------------
exit_to_user_mode_prepare
 task_work_run
  __cleanup_mnt
   cleanup_mnt
    deactivate_super
     deactivate_locked_super
      kill_block_super
       generic_shutdown_super
        shrink_dcache_for_umount
         dentry = sb->s_root
         sb->s_root = NULL              <--- Here set NULL
        sync_filesystem
         __sync_filesystem
          sb->s_op->sync_fs > ext4_sync_fs
           dquot_writeback_dquots
            sb->dq_op->write_info > ext4_write_info
             ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)
              d_inode(sb->s_root)
               s_root->d_inode          <--- Null pointer dereference

To solve this problem, we use ext4_journal_start_sb directly
to avoid s_root being used.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
---
 fs/ext4/super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9a66abcca1a8..0ce4565422f6 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type)
 	handle_t *handle;
 
 	/* Data block + inode block */
-	handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2);
+	handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 	ret = dquot_commit_info(sb, type);
-- 
2.31.1


^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH] ext4: fix null-ptr-deref in ext4_write_info
  2022-08-05 12:39 [PATCH] ext4: fix null-ptr-deref in ext4_write_info Baokun Li
@ 2022-08-05 13:07 ` Lukas Czerner
  2022-08-10  7:20   ` Baokun Li
  2022-09-27 21:53 ` Theodore Ts'o
  1 sibling, 1 reply; 5+ messages in thread
From: Lukas Czerner @ 2022-08-05 13:07 UTC (permalink / raw)
  To: Baokun Li
  Cc: linux-ext4, tytso, adilger.kernel, jack, ritesh.list, enwlinux,
	linux-kernel, yi.zhang, yebin10, yukuai3

On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote:
> I caught a null-ptr-deref bug as follows:
> ==================================================================
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
> RIP: 0010:ext4_write_info+0x53/0x1b0
> [...]
> Call Trace:
>  dquot_writeback_dquots+0x341/0x9a0
>  ext4_sync_fs+0x19e/0x800
>  __sync_filesystem+0x83/0x100
>  sync_filesystem+0x89/0xf0
>  generic_shutdown_super+0x79/0x3e0
>  kill_block_super+0xa1/0x110
>  deactivate_locked_super+0xac/0x130
>  deactivate_super+0xb6/0xd0
>  cleanup_mnt+0x289/0x400
>  __cleanup_mnt+0x16/0x20
>  task_work_run+0x11c/0x1c0
>  exit_to_user_mode_prepare+0x203/0x210
>  syscall_exit_to_user_mode+0x5b/0x3a0
>  do_syscall_64+0x59/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  ==================================================================
> 
> Above issue may happen as follows:
> -------------------------------------
> exit_to_user_mode_prepare
>  task_work_run
>   __cleanup_mnt
>    cleanup_mnt
>     deactivate_super
>      deactivate_locked_super
>       kill_block_super
>        generic_shutdown_super
>         shrink_dcache_for_umount
>          dentry = sb->s_root
>          sb->s_root = NULL              <--- Here set NULL
>         sync_filesystem
>          __sync_filesystem
>           sb->s_op->sync_fs > ext4_sync_fs
>            dquot_writeback_dquots
>             sb->dq_op->write_info > ext4_write_info
>              ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)
>               d_inode(sb->s_root)
>                s_root->d_inode          <--- Null pointer dereference
> 
> To solve this problem, we use ext4_journal_start_sb directly
> to avoid s_root being used.

Are we syncing the file system after the superblock shutdown and getting
away with it? This does not look good. Do you have a reproducer?

Thanks!
-Lukas

> 
> Signed-off-by: Baokun Li <libaokun1@huawei.com>
> ---
>  fs/ext4/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 9a66abcca1a8..0ce4565422f6 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type)
>  	handle_t *handle;
>  
>  	/* Data block + inode block */
> -	handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2);
> +	handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2);
>  	if (IS_ERR(handle))
>  		return PTR_ERR(handle);
>  	ret = dquot_commit_info(sb, type);
> -- 
> 2.31.1
> 


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] ext4: fix null-ptr-deref in ext4_write_info
  2022-08-05 13:07 ` Lukas Czerner
@ 2022-08-10  7:20   ` Baokun Li
  2022-08-15 15:34     ` Jan Kara
  0 siblings, 1 reply; 5+ messages in thread
From: Baokun Li @ 2022-08-10  7:20 UTC (permalink / raw)
  To: Lukas Czerner
  Cc: linux-ext4, tytso, adilger.kernel, jack, ritesh.list, enwlinux,
	linux-kernel, yi.zhang, yebin10, yukuai3, Baokun Li

在 2022/8/5 21:07, Lukas Czerner 写道:
> On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote:
>> I caught a null-ptr-deref bug as follows:
>> ==================================================================
>> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
>> CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
>> RIP: 0010:ext4_write_info+0x53/0x1b0
>> [...]
>> Call Trace:
>>   dquot_writeback_dquots+0x341/0x9a0
>>   ext4_sync_fs+0x19e/0x800
>>   __sync_filesystem+0x83/0x100
>>   sync_filesystem+0x89/0xf0
>>   generic_shutdown_super+0x79/0x3e0
>>   kill_block_super+0xa1/0x110
>>   deactivate_locked_super+0xac/0x130
>>   deactivate_super+0xb6/0xd0
>>   cleanup_mnt+0x289/0x400
>>   __cleanup_mnt+0x16/0x20
>>   task_work_run+0x11c/0x1c0
>>   exit_to_user_mode_prepare+0x203/0x210
>>   syscall_exit_to_user_mode+0x5b/0x3a0
>>   do_syscall_64+0x59/0x70
>>   entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>   ==================================================================
>>
>> Above issue may happen as follows:
>> -------------------------------------
>> exit_to_user_mode_prepare
>>   task_work_run
>>    __cleanup_mnt
>>     cleanup_mnt
>>      deactivate_super
>>       deactivate_locked_super
>>        kill_block_super
>>         generic_shutdown_super
>>          shrink_dcache_for_umount
>>           dentry = sb->s_root
>>           sb->s_root = NULL              <--- Here set NULL
>>          sync_filesystem
>>           __sync_filesystem
>>            sb->s_op->sync_fs > ext4_sync_fs
>>             dquot_writeback_dquots
>>              sb->dq_op->write_info > ext4_write_info
>>               ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)
>>                d_inode(sb->s_root)
>>                 s_root->d_inode          <--- Null pointer dereference
>>
>> To solve this problem, we use ext4_journal_start_sb directly
>> to avoid s_root being used.
> Are we syncing the file system after the superblock shutdown and getting
> away with it? This does not look good. Do you have a reproducer?
>
> Thanks!
> -Lukas

Hi, Lukas!

This problem is triggered by a pressure test when I reproduce another 
problem.

So I didn't have the reproducer.

I looked at the error stack code and found that it seems there is 
something wrong.

Moreover, it's really weird to write code like 
"ext4_journal_start(d_inode(sb->s_root), ...)".

>> Signed-off-by: Baokun Li <libaokun1@huawei.com>
>> ---
>>   fs/ext4/super.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index 9a66abcca1a8..0ce4565422f6 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type)
>>   	handle_t *handle;
>>   
>>   	/* Data block + inode block */
>> -	handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2);
>> +	handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2);
>>   	if (IS_ERR(handle))
>>   		return PTR_ERR(handle);
>>   	ret = dquot_commit_info(sb, type);
>> -- 
>> 2.31.1
>>
> .


Thanks!

-- 
With Best Regards,
Baokun Li


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] ext4: fix null-ptr-deref in ext4_write_info
  2022-08-10  7:20   ` Baokun Li
@ 2022-08-15 15:34     ` Jan Kara
  0 siblings, 0 replies; 5+ messages in thread
From: Jan Kara @ 2022-08-15 15:34 UTC (permalink / raw)
  To: Baokun Li
  Cc: Lukas Czerner, linux-ext4, tytso, adilger.kernel, jack,
	ritesh.list, enwlinux, linux-kernel, yi.zhang, yebin10, yukuai3

On Wed 10-08-22 15:20:48, Baokun Li wrote:
> 在 2022/8/5 21:07, Lukas Czerner 写道:
> > On Fri, Aug 05, 2022 at 08:39:47PM +0800, Baokun Li wrote:
> > > I caught a null-ptr-deref bug as follows:
> > > ==================================================================
> > > KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> > > CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
> > > RIP: 0010:ext4_write_info+0x53/0x1b0
> > > [...]
> > > Call Trace:
> > >   dquot_writeback_dquots+0x341/0x9a0
> > >   ext4_sync_fs+0x19e/0x800
> > >   __sync_filesystem+0x83/0x100
> > >   sync_filesystem+0x89/0xf0
> > >   generic_shutdown_super+0x79/0x3e0
> > >   kill_block_super+0xa1/0x110
> > >   deactivate_locked_super+0xac/0x130
> > >   deactivate_super+0xb6/0xd0
> > >   cleanup_mnt+0x289/0x400
> > >   __cleanup_mnt+0x16/0x20
> > >   task_work_run+0x11c/0x1c0
> > >   exit_to_user_mode_prepare+0x203/0x210
> > >   syscall_exit_to_user_mode+0x5b/0x3a0
> > >   do_syscall_64+0x59/0x70
> > >   entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > >   ==================================================================
> > > 
> > > Above issue may happen as follows:
> > > -------------------------------------
> > > exit_to_user_mode_prepare
> > >   task_work_run
> > >    __cleanup_mnt
> > >     cleanup_mnt
> > >      deactivate_super
> > >       deactivate_locked_super
> > >        kill_block_super
> > >         generic_shutdown_super
> > >          shrink_dcache_for_umount
> > >           dentry = sb->s_root
> > >           sb->s_root = NULL              <--- Here set NULL
> > >          sync_filesystem
> > >           __sync_filesystem
> > >            sb->s_op->sync_fs > ext4_sync_fs
> > >             dquot_writeback_dquots
> > >              sb->dq_op->write_info > ext4_write_info
> > >               ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2)
> > >                d_inode(sb->s_root)
> > >                 s_root->d_inode          <--- Null pointer dereference
> > > 
> > > To solve this problem, we use ext4_journal_start_sb directly
> > > to avoid s_root being used.
> > Are we syncing the file system after the superblock shutdown and getting
> > away with it? This does not look good. Do you have a reproducer?
> > 
> > Thanks!
> > -Lukas
> 
> Hi, Lukas!
> 
> This problem is triggered by a pressure test when I reproduce another
> problem.
> 
> So I didn't have the reproducer.
> 
> I looked at the error stack code and found that it seems there is something
> wrong.
> 
> Moreover, it's really weird to write code like
> "ext4_journal_start(d_inode(sb->s_root), ...)".

I agree. That looks like some leftover from the past. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
> > > Signed-off-by: Baokun Li <libaokun1@huawei.com>
> > > ---
> > >   fs/ext4/super.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > > index 9a66abcca1a8..0ce4565422f6 100644
> > > --- a/fs/ext4/super.c
> > > +++ b/fs/ext4/super.c
> > > @@ -6653,7 +6653,7 @@ static int ext4_write_info(struct super_block *sb, int type)
> > >   	handle_t *handle;
> > >   	/* Data block + inode block */
> > > -	handle = ext4_journal_start(d_inode(sb->s_root), EXT4_HT_QUOTA, 2);
> > > +	handle = ext4_journal_start_sb(sb, EXT4_HT_QUOTA, 2);
> > >   	if (IS_ERR(handle))
> > >   		return PTR_ERR(handle);
> > >   	ret = dquot_commit_info(sb, type);
> > > -- 
> > > 2.31.1
> > > 
> > .
> 
> 
> Thanks!
> 
> -- 
> With Best Regards,
> Baokun Li
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH] ext4: fix null-ptr-deref in ext4_write_info
  2022-08-05 12:39 [PATCH] ext4: fix null-ptr-deref in ext4_write_info Baokun Li
  2022-08-05 13:07 ` Lukas Czerner
@ 2022-09-27 21:53 ` Theodore Ts'o
  1 sibling, 0 replies; 5+ messages in thread
From: Theodore Ts'o @ 2022-09-27 21:53 UTC (permalink / raw)
  To: libaokun1, linux-ext4
  Cc: Theodore Ts'o, lczerner, yebin10, ritesh.list, yi.zhang,
	jack, linux-kernel, yukuai3, adilger.kernel, enwlinux

On Fri, 5 Aug 2022 20:39:47 +0800, Baokun Li wrote:
> I caught a null-ptr-deref bug as follows:
> ==================================================================
> KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
> CPU: 1 PID: 1589 Comm: umount Not tainted 5.10.0-02219-dirty #339
> RIP: 0010:ext4_write_info+0x53/0x1b0
> [...]
> Call Trace:
>  dquot_writeback_dquots+0x341/0x9a0
>  ext4_sync_fs+0x19e/0x800
>  __sync_filesystem+0x83/0x100
>  sync_filesystem+0x89/0xf0
>  generic_shutdown_super+0x79/0x3e0
>  kill_block_super+0xa1/0x110
>  deactivate_locked_super+0xac/0x130
>  deactivate_super+0xb6/0xd0
>  cleanup_mnt+0x289/0x400
>  __cleanup_mnt+0x16/0x20
>  task_work_run+0x11c/0x1c0
>  exit_to_user_mode_prepare+0x203/0x210
>  syscall_exit_to_user_mode+0x5b/0x3a0
>  do_syscall_64+0x59/0x70
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>  ==================================================================
> 
> [...]

Applied, thanks!

[1/1] ext4: fix null-ptr-deref in ext4_write_info
      commit: 647642bf8f326994d7eaf785bba3fa9dad92cff0

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2022-09-27 21:54 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-08-05 12:39 [PATCH] ext4: fix null-ptr-deref in ext4_write_info Baokun Li
2022-08-05 13:07 ` Lukas Czerner
2022-08-10  7:20   ` Baokun Li
2022-08-15 15:34     ` Jan Kara
2022-09-27 21:53 ` Theodore Ts'o

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