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 abhishek.shah@columbia.edu 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 783d0cd4fcbd..3a5f5bcedb3b 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -3318,12 +3318,16 @@ 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) @@ -3331,7 +3335,8 @@ 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);
@@ -3347,7 +3352,8 @@ 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);