[PATCH 5.18 64/88] ipv4: Fix data-races around sysctl_fib_notify_on_flag_change.

Greg Kroah-Hartman
2022-08-01T12:19:54Z

From: Kuniyuki Iwashima <kuniyu@amazon.com>

[ Upstream commit 96b9bd8c6d125490f9adfb57d387ef81a55a103e ]

While reading sysctl_fib_notify_on_flag_change, it can be changed
concurrently. Thus, we need to add READ_ONCE() to its readers.

Fixes: 680aea08e78c ("net: ipv4: Emit notification when fib hardware flags are changed")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/fib_trie.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 43a496272227..c1b53854047b 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1042,6 +1042,7 @@ fib_find_matching_alias(struct net *net, const struct fib_rt_info *fri)

void fib_alias_hw_flags_set(struct net *net, const struct fib_rt_info *fri)
{
+ u8 fib_notify_on_flag_change;
struct fib_alias *fa_match;
struct sk_buff *skb;
int err;
@@ -1063,14 +1064,16 @@ void fib_alias_hw_flags_set(struct net *net, const struct fib_rt_info *fri)
WRITE_ONCE(fa_match->offload, fri->offload);
WRITE_ONCE(fa_match->trap, fri->trap);

+ fib_notify_on_flag_change = READ_ONCE(net->ipv4.sysctl_fib_notify_on_flag_change);
+
/* 2 means send notifications only if offload_failed was changed. */
- if (net->ipv4.sysctl_fib_notify_on_flag_change == 2 &&
+ if (fib_notify_on_flag_change == 2 &&
READ_ONCE(fa_match->offload_failed) == fri->offload_failed)
goto out;

WRITE_ONCE(fa_match->offload_failed, fri->offload_failed);

- if (!net->ipv4.sysctl_fib_notify_on_flag_change)
+ if (!fib_notify_on_flag_change)
goto out;

skb = nlmsg_new(fib_nlmsg_size(fa_match->fa_info), GFP_ATOMIC);
--
2.35.1