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    Subject[PATCH 4.19 105/195] jbd2_seq_info_next should increase position index
    Date
    From: Vasily Averin <vvs@virtuozzo.com>

    commit 1a8e9cf40c9a6a2e40b1e924b13ed303aeea4418 upstream.

    if seq_file .next fuction does not change position index,
    read after some lseek can generate unexpected output.

    Script below generates endless output
    $ q=;while read -r r;do echo "$((++q)) $r";done </proc/fs/jbd2/DEV/info

    https://bugzilla.kernel.org/show_bug.cgi?id=206283

    Fixes: 1f4aace60b0e ("fs/seq_file.c: simplify seq_file iteration code and interface")
    Cc: stable@kernel.org
    Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
    Reviewed-by: Jan Kara <jack@suse.cz>
    Link: https://lore.kernel.org/r/d13805e5-695e-8ac3-b678-26ca2313629f@virtuozzo.com
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/jbd2/journal.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/fs/jbd2/journal.c
    +++ b/fs/jbd2/journal.c
    @@ -1002,6 +1002,7 @@ static void *jbd2_seq_info_start(struct

    static void *jbd2_seq_info_next(struct seq_file *seq, void *v, loff_t *pos)
    {
    + (*pos)++;
    return NULL;
    }


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