[PATCH 6.1.y] f2fs: avoid dead loop in f2fs_issue_checkpoint()

[PATCH 6.1.y] f2fs: avoid dead loop in f2fs_issue_checkpoint()

[Sergio González Collado]

From: Chao Yu <chao@kernel.org>

[ Upstream commit 5079e1c0c879311668b77075de3e701869804adf ]

generic/082 reports a bug as below:

__schedule+0x332/0xf60
schedule+0x6f/0xf0
schedule_timeout+0x23b/0x2a0
wait_for_completion+0x8f/0x140
f2fs_issue_checkpoint+0xfe/0x1b0
f2fs_sync_fs+0x9d/0xb0
sync_filesystem+0x87/0xb0
dquot_load_quota_sb+0x41b/0x460
dquot_load_quota_inode+0xa5/0x130
dquot_quota_on+0x4b/0x60
f2fs_quota_on+0xe3/0x1b0
do_quotactl+0x483/0x700
__x64_sys_quotactl+0x15c/0x310
do_syscall_64+0x3f/0x90
entry_SYSCALL_64_after_hwframe+0x72/0xdc

The root casue is race case as below:

Thread A			Kworker			IRQ
- write()
: write data to quota.user file

				- writepages
				 - f2fs_submit_page_write
				  - __is_cp_guaranteed return false
				  - inc_page_count(F2FS_WB_DATA)
				 - submit_bio
- quotactl(Q_QUOTAON)
 - f2fs_quota_on
  - dquot_quota_on
   - dquot_load_quota_inode
    - vfs_setup_quota_inode
    : inode->i_flags |= S_NOQUOTA
							- f2fs_write_end_io
							 - __is_cp_guaranteed return true
							 - dec_page_count(F2FS_WB_CP_DATA)
    - dquot_load_quota_sb
     - f2fs_sync_fs
      - f2fs_issue_checkpoint
       - do_checkpoint
        - f2fs_wait_on_all_pages(F2FS_WB_CP_DATA)
        : loop due to F2FS_WB_CP_DATA count is negative

Calling filemap_fdatawrite() and filemap_fdatawait() to keep all data
clean before quota file setup.

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
(cherry picked from commit 5079e1c0c879311668b77075de3e701869804adf)
Signed-off-by: Sergio González Collado <sergio.collado@gmail.com>
Reported-by: syzbot+d0ab8746c920a592aeab@syzkaller.appspotmail.com
---
 fs/f2fs/super.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 6bd8c231069a..2d586a6bfe5f 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -2824,15 +2824,26 @@ static int f2fs_quota_on(struct super_block *sb, int type, int format_id,
 		return -EBUSY;
 	}
 
+	if (path->dentry->d_sb != sb)
+		return -EXDEV;
+
 	err = f2fs_quota_sync(sb, type);
 	if (err)
 		return err;
 
-	err = dquot_quota_on(sb, type, format_id, path);
+	inode = d_inode(path->dentry);
+
+	err = filemap_fdatawrite(inode->i_mapping);
 	if (err)
 		return err;
 
-	inode = d_inode(path->dentry);
+	err = filemap_fdatawait(inode->i_mapping);
+	if (err)
+		return err;
+
+	err = dquot_quota_on(sb, type, format_id, path);
+	if (err)
+		return err;
 
 	inode_lock(inode);
 	F2FS_I(inode)->i_flags |= F2FS_NOATIME_FL | F2FS_IMMUTABLE_FL;
-- 
2.39.2

Re: [PATCH 6.1.y] f2fs: avoid dead loop in f2fs_issue_checkpoint()

[Greg KH]

On Thu, Jul 25, 2024 at 01:19:33PM +0200, Sergio González Collado wrote:
> From: Chao Yu <chao@kernel.org>
> 
> [ Upstream commit 5079e1c0c879311668b77075de3e701869804adf ]
> 
> generic/082 reports a bug as below:
> 
> __schedule+0x332/0xf60
> schedule+0x6f/0xf0
> schedule_timeout+0x23b/0x2a0
> wait_for_completion+0x8f/0x140
> f2fs_issue_checkpoint+0xfe/0x1b0
> f2fs_sync_fs+0x9d/0xb0
> sync_filesystem+0x87/0xb0
> dquot_load_quota_sb+0x41b/0x460
> dquot_load_quota_inode+0xa5/0x130
> dquot_quota_on+0x4b/0x60
> f2fs_quota_on+0xe3/0x1b0
> do_quotactl+0x483/0x700
> __x64_sys_quotactl+0x15c/0x310
> do_syscall_64+0x3f/0x90
> entry_SYSCALL_64_after_hwframe+0x72/0xdc
> 
> The root casue is race case as below:
> 
> Thread A			Kworker			IRQ
> - write()
> : write data to quota.user file
> 
> 				- writepages
> 				 - f2fs_submit_page_write
> 				  - __is_cp_guaranteed return false
> 				  - inc_page_count(F2FS_WB_DATA)
> 				 - submit_bio
> - quotactl(Q_QUOTAON)
>  - f2fs_quota_on
>   - dquot_quota_on
>    - dquot_load_quota_inode
>     - vfs_setup_quota_inode
>     : inode->i_flags |= S_NOQUOTA
> 							- f2fs_write_end_io
> 							 - __is_cp_guaranteed return true
> 							 - dec_page_count(F2FS_WB_CP_DATA)
>     - dquot_load_quota_sb
>      - f2fs_sync_fs
>       - f2fs_issue_checkpoint
>        - do_checkpoint
>         - f2fs_wait_on_all_pages(F2FS_WB_CP_DATA)
>         : loop due to F2FS_WB_CP_DATA count is negative
> 
> Calling filemap_fdatawrite() and filemap_fdatawait() to keep all data
> clean before quota file setup.
> 
> Signed-off-by: Chao Yu <chao@kernel.org>
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> (cherry picked from commit 5079e1c0c879311668b77075de3e701869804adf)
> Signed-off-by: Sergio González Collado <sergio.collado@gmail.com>
> Reported-by: syzbot+d0ab8746c920a592aeab@syzkaller.appspotmail.com
> ---
>  fs/f2fs/super.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)

Now queued up, thanks.

greg k-h