Patch "sysctl: Fix data-races in proc_dou8vec_minmax()." has been added to the 5.18-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    sysctl: Fix data-races in proc_dou8vec_minmax().

to the 5.18-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:
     sysctl-fix-data-races-in-proc_dou8vec_minmax.patch
and it can be found in the queue-5.18 subdirectory.

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



commit 9972fe50cd98fd1d3ba3f13274413043a869cea5
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date:   Mon Jul 11 17:15:19 2022 -0700

    sysctl: Fix data-races in proc_dou8vec_minmax().
    
    [ Upstream commit 7dee5d7747a69aa2be41f04c6a7ecfe3ac8cdf18 ]
    
    A sysctl variable is accessed concurrently, and there is always a chance
    of data-race.  So, all readers and writers need some basic protection to
    avoid load/store-tearing.
    
    This patch changes proc_dou8vec_minmax() to use READ_ONCE() and
    WRITE_ONCE() internally to fix data-races on the sysctl side.  For now,
    proc_dou8vec_minmax() itself is tolerant to a data-race, but we still
    need to add annotations on the other subsystem's side.
    
    Fixes: cb9444130662 ("sysctl: add proc_dou8vec_minmax()")
    Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 878b1122cb89..54ec36e69907 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1079,13 +1079,13 @@ int proc_dou8vec_minmax(struct ctl_table *table, int write,
 
 	tmp.maxlen = sizeof(val);
 	tmp.data = &val;
-	val = *data;
+	val = READ_ONCE(*data);
 	res = do_proc_douintvec(&tmp, write, buffer, lenp, ppos,
 				do_proc_douintvec_minmax_conv, &param);
 	if (res)
 		return res;
 	if (write)
-		*data = val;
+		WRITE_ONCE(*data, val);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(proc_dou8vec_minmax);