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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> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- fs/jbd2/journal.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index 5577e0df..0e42d26 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -987,6 +987,7 @@ static void *jbd2_seq_info_start(struct seq_file *seq, loff_t *pos) static void *jbd2_seq_info_next(struct seq_file *seq, void *v, loff_t *pos) { + (*pos)++; return NULL; } -- 1.8.3