[PATCH AUTOSEL 6.0 13/77] tcp: annotate data-race around tcp_md5sig_pool_populated
From: Sasha Levin <sashal@kernel.org>
Date: 2022-10-09 22:09:47
Also in:
lkml, stable
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Eric Dumazet <edumazet@google.com> [ Upstream commit aacd467c0a576e5e44d2de4205855dc0fe43f6fb ] tcp_md5sig_pool_populated can be read while another thread changes its value. The race has no consequence because allocations are protected with tcp_md5sig_mutex. This patch adds READ_ONCE() and WRITE_ONCE() to document the race and silence KCSAN. Reported-by: Abhishek Shah <redacted> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org> --- net/ipv4/tcp.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e373dde1f46f..3733742cebf8 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c@@ -4442,12 +4442,16 @@ static void __tcp_alloc_md5sig_pool(void) * to memory. See smp_rmb() in tcp_get_md5sig_pool() */ smp_wmb(); - tcp_md5sig_pool_populated = true; + /* Paired with READ_ONCE() from tcp_alloc_md5sig_pool() + * and tcp_get_md5sig_pool(). + */ + WRITE_ONCE(tcp_md5sig_pool_populated, true); } bool tcp_alloc_md5sig_pool(void) { - if (unlikely(!tcp_md5sig_pool_populated)) { + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + if (unlikely(!READ_ONCE(tcp_md5sig_pool_populated))) { mutex_lock(&tcp_md5sig_mutex); if (!tcp_md5sig_pool_populated) {
@@ -4458,7 +4462,8 @@ bool tcp_alloc_md5sig_pool(void) mutex_unlock(&tcp_md5sig_mutex); } - return tcp_md5sig_pool_populated; + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + return READ_ONCE(tcp_md5sig_pool_populated); } EXPORT_SYMBOL(tcp_alloc_md5sig_pool);
@@ -4474,7 +4479,8 @@ struct tcp_md5sig_pool *tcp_get_md5sig_pool(void) { local_bh_disable(); - if (tcp_md5sig_pool_populated) { + /* Paired with WRITE_ONCE() from __tcp_alloc_md5sig_pool() */ + if (READ_ONCE(tcp_md5sig_pool_populated)) { /* coupled with smp_wmb() in __tcp_alloc_md5sig_pool() */ smp_rmb(); return this_cpu_ptr(&tcp_md5sig_pool);
--
2.35.1