linux-kernel - Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get

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Message-ID: <20250628120413.3247-1-enjuk@amazon.com>
Date: Sat, 28 Jun 2025 21:04:03 +0900
From: Kohei Enju <enjuk@...zon.com>
To: <syzbot+e04e2c007ba2c80476cb@...kaller.appspotmail.com>
CC: <linux-kernel@...r.kernel.org>, <syzkaller-bugs@...glegroups.com>,
	<kohei.enju@...il.com>
Subject: Re: [syzbot] [hams?] KASAN: slab-use-after-free Read in rose_get_neigh

#syz test

diff --git a/net/rose/rose_route.c b/net/rose/rose_route.c
index 2dd6bd3a3011..b72bf8a08d48 100644
--- a/net/rose/rose_route.c
+++ b/net/rose/rose_route.c
@@ -497,22 +497,15 @@ void rose_rt_device_down(struct net_device *dev)
 			t         = rose_node;
 			rose_node = rose_node->next;
 
-			for (i = 0; i < t->count; i++) {
+			for (i = t->count - 1; i >= 0; i--) {
 				if (t->neighbour[i] != s)
 					continue;
 
 				t->count--;
 
-				switch (i) {
-				case 0:
-					t->neighbour[0] = t->neighbour[1];
-					fallthrough;
-				case 1:
-					t->neighbour[1] = t->neighbour[2];
-					break;
-				case 2:
-					break;
-				}
+				memmove(&t->neighbour[i], &t->neighbour[i + 1],
+					sizeof(t->neighbour[0]) *
+						(t->count - i));
 			}
 
 			if (t->count <= 0)