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

[Julian Anastasov <ja@ssi.bg>]

	Hello,

On Mon, 21 Aug 2023, gregkh@linuxfoundation.org wrote:

> 
> 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@vger.kernel.org>.
> 
> 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@vger.kernel.org>' --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")

	It can happen only if we backport the other mentioned
commit 1b90af292e71 which needs changing SYSCTL_ZERO/SYSCTL_ONE
to zero/one and then 5310760af1d4 will apply as-is to both 4.14 and
4.19. Should I send backport for 1b90af292e71, it is even more
useful as a fix than 5310760af1d4?

> thanks,
> 
> greg k-h
> 
> ------------------ original commit in Linus's tree ------------------
> 
> >From 5310760af1d4fbea1452bfc77db5f9a680f7ae47 Mon Sep 17 00:00:00 2001
> From: Sishuai Gong <sishuai.system@gmail.com>
> 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@gmail.com/
> Signed-off-by: Sishuai Gong <sishuai.system@gmail.com>
> Acked-by: Simon Horman <horms@kernel.org>
> Acked-by: Julian Anastasov <ja@ssi.bg>
> Signed-off-by: Florian Westphal <fw@strlen.de>
> 
> 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;

Regards

--
Julian Anastasov <ja@ssi.bg>