netdev - [PATCH AUTOSEL 5.4 082/330] ipv6_route_seq_next should increase position index

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Message-Id: <20200918020110.2063155-82-sashal@kernel.org>
Date:   Thu, 17 Sep 2020 21:57:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Vasily Averin <vvs@...tuozzo.com>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 082/330] ipv6_route_seq_next should increase position index

From: Vasily Averin <vvs@...tuozzo.com>

[ Upstream commit 4fc427e0515811250647d44de38d87d7b0e0790f ]

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@...tuozzo.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/ipv6/ip6_fib.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index 7a0c877ca306c..7662de1bd7fd2 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -2474,14 +2474,13 @@ static void *ipv6_route_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 	struct net *net = seq_file_net(seq);
 	struct ipv6_route_iter *iter = seq->private;
 
+	++(*pos);
 	if (!v)
 		goto iter_table;
 
 	n = rcu_dereference_bh(((struct fib6_info *)v)->fib6_next);
-	if (n) {
-		++*pos;
+	if (n)
 		return n;
-	}
 
 iter_table:
 	ipv6_route_check_sernum(iter);
@@ -2489,8 +2488,6 @@ iter_table:
 	r = fib6_walk_continue(&iter->w);
 	spin_unlock_bh(&iter->tbl->tb6_lock);
 	if (r > 0) {
-		if (v)
-			++*pos;
 		return iter->w.leaf;
 	} else if (r < 0) {
 		fib6_walker_unlink(net, &iter->w);
-- 
2.25.1