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tcp: annotate data-race around tcp_md5sig_pool_populated 

[ Upstream commit aacd467c0a ]

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>
This commit is contained in:
Eric Dumazet 2022-08-22 21:15:28 +00:00 committed by Greg Kroah-Hartman
parent 840ebe769f
commit 7afdf41db8
1 changed files with 10 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
net/ipv4/tcp.c
View File

@ -4444,12 +4444,16 @@ 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) {
@ -4460,7 +4464,8 @@ 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);
@ -4476,7 +4481,8 @@ 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);