From: Vasily Averin <vvs@xxxxxxxxxxxxx> 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@xxxxxxxxxx Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx> Reviewed-by: Jan Kara <jack@xxxxxxx> Link: https://lore.kernel.org/r/d13805e5-695e-8ac3-b678-26ca2313629f@xxxxxxxxxxxxx Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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; }
