Patch "tcp: annotate data races in __tcp_oow_rate_limited()" has been added to the 4.19-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



This is a note to let you know that I've just added the patch titled

    tcp: annotate data races in __tcp_oow_rate_limited()

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-annotate-data-races-in-__tcp_oow_rate_limited.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 36d7bf742ab5800923fe42f090516a1a2792401c
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Thu Jun 29 16:41:50 2023 +0000

    tcp: annotate data races in __tcp_oow_rate_limited()
    
    [ Upstream commit 998127cdb4699b9d470a9348ffe9f1154346be5f ]
    
    request sockets are lockless, __tcp_oow_rate_limited() could be called
    on the same object from different cpus. This is harmless.
    
    Add READ_ONCE()/WRITE_ONCE() annotations to avoid a KCSAN report.
    
    Fixes: 4ce7e93cb3fe ("tcp: rate limit ACK sent by SYN_RECV request sockets")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index bd921fa7b9ab4..281f7799aeafc 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3429,8 +3429,11 @@ static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32
 static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,
 				   u32 *last_oow_ack_time)
 {
-	if (*last_oow_ack_time) {
-		s32 elapsed = (s32)(tcp_jiffies32 - *last_oow_ack_time);
+	/* Paired with the WRITE_ONCE() in this function. */
+	u32 val = READ_ONCE(*last_oow_ack_time);
+
+	if (val) {
+		s32 elapsed = (s32)(tcp_jiffies32 - val);
 
 		if (0 <= elapsed &&
 		    elapsed < READ_ONCE(net->ipv4.sysctl_tcp_invalid_ratelimit)) {
@@ -3439,7 +3442,10 @@ static bool __tcp_oow_rate_limited(struct net *net, int mib_idx,
 		}
 	}
 
-	*last_oow_ack_time = tcp_jiffies32;
+	/* Paired with the prior READ_ONCE() and with itself,
+	 * as we might be lockless.
+	 */
+	WRITE_ONCE(*last_oow_ack_time, tcp_jiffies32);
 
 	return false;	/* not rate-limited: go ahead, send dupack now! */
 }



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux