netdev - [PATCH net] net: Properly typecast int values to set sk_max_pacing

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Date:   Mon, 19 Oct 2020 20:31:49 -0400
From:   Ke Li <keli@...mai.com>
To:     <netdev@...r.kernel.org>
CC:     <davem@...emloft.net>, <kuba@...nel.org>, <edumazet@...gle.com>,
        <kli@...l.edu>, Ke Li <keli@...mai.com>, Ji Li <jli@...mai.com>
Subject: [PATCH net] net: Properly typecast int values to set sk_max_pacing_rate

In setsockopt(SO_MAX_PACING_RATE) on 64bit systems, sk_max_pacing_rate,
after extended from 'u32' to 'unsigned long', takes unintentionally
hiked value whenever assigned from an 'int' value with MSB=1, due to
binary sign extension in promoting s32 to u64, e.g. 0x80000000 becomes
0xFFFFFFFF80000000.

Thus inflated sk_max_pacing_rate causes subsequent getsockopt to return
~0U unexpectedly. It may also result in increased pacing rate.

Fix by explicitly casting the 'int' value to 'unsigned int' before
assigning it to sk_max_pacing_rate, for zero extension to happen.

Fixes: 76a9ebe811fb ("net: extend sk_pacing_rate to unsigned long")
Signed-off-by: Ji Li <jli@...mai.com>
Signed-off-by: Ke Li <keli@...mai.com>
Cc: Eric Dumazet <edumazet@...gle.com>
---
 net/core/filter.c | 2 +-
 net/core/sock.c   | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index c5e2a1c5fd8d..43f20c14864c 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4693,7 +4693,7 @@ static int _bpf_setsockopt(struct sock *sk, int level, int optname,
 				cmpxchg(&sk->sk_pacing_status,
 					SK_PACING_NONE,
 					SK_PACING_NEEDED);
-			sk->sk_max_pacing_rate = (val == ~0U) ? ~0UL : val;
+			sk->sk_max_pacing_rate = (val == ~0U) ? ~0UL : (unsigned int)val;
 			sk->sk_pacing_rate = min(sk->sk_pacing_rate,
 						 sk->sk_max_pacing_rate);
 			break;
diff --git a/net/core/sock.c b/net/core/sock.c
index 4e8729357122..727ea1cc633c 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1163,7 +1163,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 
 	case SO_MAX_PACING_RATE:
 		{
-		unsigned long ulval = (val == ~0U) ? ~0UL : val;
+		unsigned long ulval = (val == ~0U) ? ~0UL : (unsigned int)val;
 
 		if (sizeof(ulval) != sizeof(val) &&
 		    optlen >= sizeof(ulval) &&

base-commit: 0e8b8d6a2d85344d80dda5beadd98f5f86e8d3d3
-- 
2.17.1