Patch "sock: annotate data-races around prot->memory_pressure" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    sock: annotate data-races around prot->memory_pressure

to the 6.1-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:
     sock-annotate-data-races-around-prot-memory_pressure.patch
and it can be found in the queue-6.1 subdirectory.

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



commit 1a64ec3477bc57c27c4bb8bdd3a128cce0dbe176
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date:   Fri Aug 18 01:51:32 2023 +0000

    sock: annotate data-races around prot->memory_pressure
    
    [ Upstream commit 76f33296d2e09f63118db78125c95ef56df438e9 ]
    
    *prot->memory_pressure is read/writen locklessly, we need
    to add proper annotations.
    
    A recent commit added a new race, it is time to audit all accesses.
    
    Fixes: 2d0c88e84e48 ("sock: Fix misuse of sk_under_memory_pressure()")
    Fixes: 4d93df0abd50 ("[SCTP]: Rewrite of sctp buffer management code")
    Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
    Cc: Abel Wu <wuyun.abel@xxxxxxxxxxxxx>
    Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230818015132.2699348-1-edumazet@xxxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/include/net/sock.h b/include/net/sock.h
index 699408944952c..d1f936ed97556 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1320,6 +1320,7 @@ struct proto {
 	/*
 	 * Pressure flag: try to collapse.
 	 * Technical note: it is used by multiple contexts non atomically.
+	 * Make sure to use READ_ONCE()/WRITE_ONCE() for all reads/writes.
 	 * All the __sk_mem_schedule() is of this nature: accounting
 	 * is strict, actions are advisory and have some latency.
 	 */
@@ -1448,7 +1449,7 @@ static inline bool sk_has_memory_pressure(const struct sock *sk)
 static inline bool sk_under_global_memory_pressure(const struct sock *sk)
 {
 	return sk->sk_prot->memory_pressure &&
-		!!*sk->sk_prot->memory_pressure;
+		!!READ_ONCE(*sk->sk_prot->memory_pressure);
 }
 
 static inline bool sk_under_memory_pressure(const struct sock *sk)
@@ -1460,7 +1461,7 @@ static inline bool sk_under_memory_pressure(const struct sock *sk)
 	    mem_cgroup_under_socket_pressure(sk->sk_memcg))
 		return true;
 
-	return !!*sk->sk_prot->memory_pressure;
+	return !!READ_ONCE(*sk->sk_prot->memory_pressure);
 }
 
 static inline long
@@ -1537,7 +1538,7 @@ proto_memory_pressure(struct proto *prot)
 {
 	if (!prot->memory_pressure)
 		return false;
-	return !!*prot->memory_pressure;
+	return !!READ_ONCE(*prot->memory_pressure);
 }
 
 
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index c806d272107ac..83656fe03a0e6 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -98,7 +98,7 @@ struct percpu_counter sctp_sockets_allocated;
 
 static void sctp_enter_memory_pressure(struct sock *sk)
 {
-	sctp_memory_pressure = 1;
+	WRITE_ONCE(sctp_memory_pressure, 1);
 }