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Date: Thu, 16 May 2024 16:40:56 +0800
From: sunshijie <sunshijie@...omi.corp-partner.google.com>
To: jaegeuk@...nel.org,
	chao@...nel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Cc: sunshijie <sunshijie@...omi.com>
Subject: [PATCH] f2fs: fix panic in f2fs_put_super

When thread A calls kill_f2fs_super, thread A may submit a bio to the function iput(sbi->node_inode);
Then thread A enters the process D state, and thread B may also call kill_f2fs_super and execute the code sbi->node_inode = NULL;
Now that the bio submitted by thread A is complete, it calls f2fs_write_end_io and may trigger null-ptr-deref in NODE_MAPPING.

Thread A                                          Thread B                         IRQ context
- f2fs_put_super
 - iput(sbi->node_inode)
  - iput_final
   - write_inode_now
    - writeback_single_inode
     - __writeback_single_inode
      - filemap_fdatawait
       - filemap_fdatawait_range
        - __kcfi_typeid_free_transhuge_page
         - __filemap_fdatawait_range
          - wait_on_page_writeback
           - folio_wait_writeback
            - folio_wait_bit
             - folio_wait_bit_common
              - io_schedule
                                                  - f2fs_put_super
                                                   - sbi->node_inode = NULL
                                                                                   - __handle_irq_event_percpu
                                                                                    - ufs_qcom_mcq_esi_handler
                                                                                     - ufshcd_mcq_poll_cqe_nolock
                                                                                      - ufshcd_compl_one_cqe
                                                                                       - scsi_done
                                                                                        - scsi_done_internal
                                                                                         - blk_mq_complete_request
                                                                                          - scsi_complete
                                                                                           - scsi_finish_command
                                                                                            - scsi_io_completion
                                                                                             - scsi_end_request
                                                                                              - blk_update_request
                                                                                               - bio_endio
                                                                                                - f2fs_write_end_io
                                                                                                 - NODE_MAPPING(sbi)

Signed-off-by: sunshijie <sunshijie@...omi.com>
---
 fs/f2fs/super.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index a4bc26dfdb1a..adffc9b80a9c 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1618,7 +1618,6 @@ static void f2fs_put_super(struct super_block *sb)
 	f2fs_release_ino_entry(sbi, true);
 
 	f2fs_leave_shrinker(sbi);
-	mutex_unlock(&sbi->umount_mutex);
 
 	/* our cp_error case, we can wait for any writeback page */
 	f2fs_flush_merged_writes(sbi);
@@ -1648,6 +1647,8 @@ static void f2fs_put_super(struct super_block *sb)
 	iput(sbi->meta_inode);
 	sbi->meta_inode = NULL;
 
+	mutex_unlock(&sbi->umount_mutex);
+
 	/*
 	 * iput() can update stat information, if f2fs_write_checkpoint()
 	 * above failed with error.
-- 
2.34.1


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