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From:   Vasily Averin <vvs@virtuozzo.com>
Subject: [PATCH 1/7] pstore_ftrace_seq_next should increase position index
To:     linux-kernel@vger.kernel.org
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        NeilBrown <neilb@suse.com>, Waiman Long <longman@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Oberparleiter <oberpar@linux.ibm.com>
Message-ID: <51376af5-e0f2-0ff2-d664-e932153b0665@virtuozzo.com>
Date:   Fri, 24 Jan 2020 10:02:42 +0300
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if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

https://bugzilla.kernel.org/show_bug.cgi?id=206283
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
---
 fs/pstore/inode.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/pstore/inode.c b/fs/pstore/inode.c
index 7fbe8f0..ea8799b 100644
--- a/fs/pstore/inode.c
+++ b/fs/pstore/inode.c
@@ -87,11 +87,11 @@ static void *pstore_ftrace_seq_next(struct seq_file *s, void *v, loff_t *pos)
 	struct pstore_private *ps = s->private;
 	struct pstore_ftrace_seq_data *data = v;
 
+	(*pos)++;
 	data->off += REC_SIZE;
 	if (data->off + REC_SIZE > ps->total_size)
 		return NULL;
 
-	(*pos)++;
 	return data;
 }
 
-- 
1.8.3.1