On 04/20/2013 06:05 AM, Alexey Khoroshilov wrote:
> If ext4_fill_super() failed after extents status shrinker
> has been registered, the shrinker is left in a global list
> while the memory, it sits in, is already freed.
> Oops is not so bad scenario after that.
> 
> Found by Linux File System Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshi...@ispras.ru>

Thanks for your patch.  This problem has been fixed in dev branch of
ext4 tree, but has not push into mainline kernel yet.  Here is the
commit id (a75ae78f087f933ab3432e98bb4dbbf2196cf6d5).

Thanks,
                                                - Zheng

> ---
>  fs/ext4/super.c |    6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 5d6d5357..5f9cb30 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3757,7 +3757,7 @@ static int ext4_fill_super(struct super_block *sb, void 
> *data, int silent)
>       if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_MMP) &&
>           !(sb->s_flags & MS_RDONLY))
>               if (ext4_multi_mount_protect(sb, le64_to_cpu(es->s_mmp_block)))
> -                     goto failed_mount3;
> +                     goto failed_mount_shr;
>  
>       /*
>        * The first inode we look at is the journal inode.  Don't try
> @@ -3766,7 +3766,7 @@ static int ext4_fill_super(struct super_block *sb, void 
> *data, int silent)
>       if (!test_opt(sb, NOLOAD) &&
>           EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL)) {
>               if (ext4_load_journal(sb, es, journal_devnum))
> -                     goto failed_mount3;
> +                     goto failed_mount_shr;
>       } else if (test_opt(sb, NOLOAD) && !(sb->s_flags & MS_RDONLY) &&
>             EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_RECOVER)) {
>               ext4_msg(sb, KERN_ERR, "required journal recovery "
> @@ -4009,6 +4009,8 @@ failed_mount_wq:
>               jbd2_journal_destroy(sbi->s_journal);
>               sbi->s_journal = NULL;
>       }
> +failed_mount_shr:
> +     ext4_es_unregister_shrinker(sb);
>  failed_mount3:
>       del_timer(&sbi->s_err_report);
>       if (sbi->s_flex_groups)
> 

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