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

Sasha Levin
2020-09-18T03:10:41Z

From: Vasily Averin <vvs@virtuozzo.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@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.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