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Commit 9060dd2c authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
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ext4: fix mmp use after free during unmount 



In ext4_put_super, we call brelse on the buffer head containing
the ext4 superblock, but then try to use it when we stop the
mmp thread, because when the thread shuts down it does:

write_mmp_block
  ext4_mmp_csum_set
    ext4_has_metadata_csum
      WARN_ON_ONCE(ext4_has_feature_metadata_csum(sb)...)

which reaches into sb->s_fs_info->s_es->s_feature_ro_compat,
which lives in the superblock buffer s_sbh which we just released.

Fix this by moving the brelse down to a point where we are no
longer using it.

Reported-by: default avatarWang Shu <shuwang@redhat.com>
Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
Reviewed-by: default avatarAndreas Dilger <adilger@dilger.ca>
parent 4f5a763c

fs/ext4/super.c

+1 −1
Original line number Diff line number Diff line
@@ -863,7 +863,6 @@ static void ext4_put_super(struct super_block *sb) 
	percpu_counter_destroy(&sbi->s_dirs_counter);

	percpu_counter_destroy(&sbi->s_dirtyclusters_counter);

	percpu_free_rwsem(&sbi->s_journal_flag_rwsem);

	brelse(sbi->s_sbh);

#ifdef CONFIG_QUOTA

	for (i = 0; i < EXT4_MAXQUOTAS; i++)

		kfree(sbi->s_qf_names[i]);
@@ -895,6 +894,7 @@ static void ext4_put_super(struct super_block *sb) 
	}

	if (sbi->s_mmp_tsk)

		kthread_stop(sbi->s_mmp_tsk);

	brelse(sbi->s_sbh);

	sb->s_fs_info = NULL;

	/*

	 * Now that we are completely done shutting down the