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Date: Mon, 16 May 2022 21:36:35 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Amit Klein <aksecurity@...il.com>, Eric Dumazet <edumazet@...gle.com>, Willy Tarreau <w@....eu>, Jakub Kicinski <kuba@...nel.org>, Sasha Levin <sashal@...nel.org> Subject: [PATCH 5.15 061/102] tcp: drop the hash_32() part from the index calculation From: Willy Tarreau <w@....eu> [ Upstream commit e8161345ddbb66e449abde10d2fdce93f867eba9 ] In commit 190cc82489f4 ("tcp: change source port randomizarion at connect() time"), the table_perturb[] array was introduced and an index was taken from the port_offset via hash_32(). But it turns out that hash_32() performs a multiplication while the input here comes from the output of SipHash in secure_seq, that is well distributed enough to avoid the need for yet another hash. Suggested-by: Amit Klein <aksecurity@...il.com> Reviewed-by: Eric Dumazet <edumazet@...gle.com> Signed-off-by: Willy Tarreau <w@....eu> Signed-off-by: Jakub Kicinski <kuba@...nel.org> Signed-off-by: Sasha Levin <sashal@...nel.org> --- net/ipv4/inet_hashtables.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c index f76e4ac1ba3a..ee9c587031b4 100644 --- a/net/ipv4/inet_hashtables.c +++ b/net/ipv4/inet_hashtables.c @@ -778,7 +778,7 @@ int __inet_hash_connect(struct inet_timewait_death_row *death_row, net_get_random_once(table_perturb, INET_TABLE_PERTURB_SIZE * sizeof(*table_perturb)); - index = hash_32(port_offset, INET_TABLE_PERTURB_SHIFT); + index = port_offset & (INET_TABLE_PERTURB_SIZE - 1); offset = READ_ONCE(table_perturb[index]) + (port_offset >> 32); offset %= remaining; -- 2.35.1
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