linux-kernel - Re: [syzbot] [mm?] BUG: unable to handle kernel paging request in list_lru

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Message-Id: <20240713090518.866-1-hdanton@sina.com>
Date: Sat, 13 Jul 2024 17:05:18 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+2403e3909382fbdeaf6c@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] BUG: unable to handle kernel paging request in list_lru_add

On Fri, 12 Jul 2024 10:11:25 -0700
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    43db1e03c086 Merge tag 'for-6.10/dm-fixes-2' of git://git...
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12b1da7e980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  43db1e03c086

--- x/mm/list_lru.c
+++ y/mm/list_lru.c
@@ -55,7 +55,8 @@ list_lru_from_memcg_idx(struct list_lru
 	if (list_lru_memcg_aware(lru) && idx >= 0) {
 		struct list_lru_memcg *mlru = xa_load(&lru->xa, idx);
 
-		return mlru ? &mlru->node[nid] : NULL;
+		if (mlru)
+			return &mlru->node[nid];
 	}
 	return &lru->node[nid].lru;
 }
--