Previous patch ("VFS: simplify seq_file iteration code and interface") removed code to set ->from to zero when ->count is zero, as ->from is dead at that time. However it didn't ensure ->from was set properly whenever ->count becomes non-zero. This can only happen when ->show() is called. Of the three places it is called one already has ->from set to zero. The other two are fixed by setting from to zero after fully flushing the buffer (at which point ->count will also be zero). Reported-by: Jann Horn Signed-off-by: NeilBrown --- fs/seq_file.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/seq_file.c b/fs/seq_file.c index fd82585ab50f..1dea7a8a5255 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c @@ -220,6 +220,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) goto Done; } /* we need at least one record in buffer */ + m->from = 0; p = m->op->start(m, &m->index); while (1) { err = PTR_ERR(p); -- 2.14.0.rc0.dirty