From ef1675823905ff09cb5e551700a124d0133648b7 Mon Sep 17 00:00:00 2001
From: Michal Kubecek <mkubecek@suse.cz>
Date: Mon, 9 Nov 2020 13:30:54 +0100
Subject: [PATCH 23/26] netlink: fix use after free in netlink_run_handler()

Valgrind detected use after free in netlink_run_handler(): some members of
struct nl_context are accessed after the netlink context is freed by
netlink_done(). Use local variables to store the two flags and check them
instead.

Fixes: 6c19c0d559c8 ("netlink: use genetlink ops information to decide about fallback")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
(cherry picked from commit 29b38ea218bd978d1950e12cc24da98215a1eeef)
---
 netlink/netlink.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/netlink/netlink.c b/netlink/netlink.c
index 86dc1efdf5ce..2a12bb8b1759 100644
--- a/netlink/netlink.c
+++ b/netlink/netlink.c
@@ -303,6 +303,7 @@ void netlink_run_handler(struct cmd_context *ctx, nl_func_t nlfunc,
 			 bool no_fallback)
 {
 	bool wildcard = ctx->devname && !strcmp(ctx->devname, WILDCARD_DEVNAME);
+	bool wildcard_unsupported, ioctl_fallback;
 	struct nl_context *nlctx;
 	const char *reason;
 	int ret;
@@ -324,14 +325,17 @@ void netlink_run_handler(struct cmd_context *ctx, nl_func_t nlfunc,
 	nlctx = ctx->nlctx;
 
 	ret = nlfunc(ctx);
+	wildcard_unsupported = nlctx->wildcard_unsupported;
+	ioctl_fallback = nlctx->ioctl_fallback;
 	netlink_done(ctx);
-	if (no_fallback || ret != -EOPNOTSUPP || !nlctx->ioctl_fallback) {
-		if (nlctx->wildcard_unsupported)
+
+	if (no_fallback || ret != -EOPNOTSUPP || !ioctl_fallback) {
+		if (wildcard_unsupported)
 			fprintf(stderr, "%s\n",
 				"subcommand does not support wildcard dump");
 		exit(ret >= 0 ? ret : 1);
 	}
-	if (nlctx->wildcard_unsupported)
+	if (wildcard_unsupported)
 		reason = "subcommand does not support wildcard dump";
 	else
 		reason = "kernel netlink support for subcommand missing";
-- 
2.26.2