Patch "sock: annotate data-races around prot->memory_pressure" has been added to the 4.19-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 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:
     sock-annotate-data-races-around-prot-memory_pressure.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 8d04eef7a3610c938737d587aa2d251bc3b6f6bc
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 bcb1901ac13a5..373e34b46a3c9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1152,6 +1152,7 @@ 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.
 	 */
@@ -1268,7 +1269,7 @@ 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)
@@ -1280,7 +1281,7 @@ 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
@@ -1334,7 +1335,7 @@ 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 baa825751c393..432dccd375064 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -112,7 +112,7 @@ 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);
 }