FAILED: patch "[PATCH] ipvs: fix racy memcpy in proc_do_sync_threshold" failed to apply to 4.19-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-4.19.y
git checkout FETCH_HEAD
git cherry-pick -x 5310760af1d4fbea1452bfc77db5f9a680f7ae47
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023082114-remix-cable-0852@gregkh' --subject-prefix 'PATCH 4.19.y' HEAD^..

Possible dependencies:

5310760af1d4 ("ipvs: fix racy memcpy in proc_do_sync_threshold")
1b90af292e71 ("ipvs: Improve robustness to the ipvs sysctl")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 5310760af1d4fbea1452bfc77db5f9a680f7ae47 Mon Sep 17 00:00:00 2001
From: Sishuai Gong <sishuai.system@xxxxxxxxx>
Date: Thu, 10 Aug 2023 15:12:42 -0400
Subject: [PATCH] ipvs: fix racy memcpy in proc_do_sync_threshold

When two threads run proc_do_sync_threshold() in parallel,
data races could happen between the two memcpy():

Thread-1			Thread-2
memcpy(val, valp, sizeof(val));
				memcpy(valp, val, sizeof(val));

This race might mess up the (struct ctl_table *) table->data,
so we add a mutex lock to serialize them.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Link: https://lore.kernel.org/netdev/B6988E90-0A1E-4B85-BF26-2DAF6D482433@xxxxxxxxx/
Signed-off-by: Sishuai Gong <sishuai.system@xxxxxxxxx>
Acked-by: Simon Horman <horms@xxxxxxxxxx>
Acked-by: Julian Anastasov <ja@xxxxxx>
Signed-off-by: Florian Westphal <fw@xxxxxxxxx>

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 62606fb44d02..4bb0d90eca1c 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -1876,6 +1876,7 @@ static int
 proc_do_sync_threshold(struct ctl_table *table, int write,
 		       void *buffer, size_t *lenp, loff_t *ppos)
 {
+	struct netns_ipvs *ipvs = table->extra2;
 	int *valp = table->data;
 	int val[2];
 	int rc;
@@ -1885,6 +1886,7 @@ proc_do_sync_threshold(struct ctl_table *table, int write,
 		.mode = table->mode,
 	};
 
+	mutex_lock(&ipvs->sync_mutex);
 	memcpy(val, valp, sizeof(val));
 	rc = proc_dointvec(&tmp, write, buffer, lenp, ppos);
 	if (write) {
@@ -1894,6 +1896,7 @@ proc_do_sync_threshold(struct ctl_table *table, int write,
 		else
 			memcpy(valp, val, sizeof(val));
 	}
+	mutex_unlock(&ipvs->sync_mutex);
 	return rc;
 }
 
@@ -4321,6 +4324,7 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
 	ipvs->sysctl_sync_threshold[0] = DEFAULT_SYNC_THRESHOLD;
 	ipvs->sysctl_sync_threshold[1] = DEFAULT_SYNC_PERIOD;
 	tbl[idx].data = &ipvs->sysctl_sync_threshold;
+	tbl[idx].extra2 = ipvs;
 	tbl[idx++].maxlen = sizeof(ipvs->sysctl_sync_threshold);
 	ipvs->sysctl_sync_refresh_period = DEFAULT_SYNC_REFRESH_PERIOD;
 	tbl[idx++].data = &ipvs->sysctl_sync_refresh_period;