linux-kernel - Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev

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Message-Id: <20240427020615.3615-1-hdanton@sina.com>
Date: Sat, 27 Apr 2024 10:06:15 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+5d34cc6474499a5ff516@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open

On Fri, 26 Apr 2024 05:00:21 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    e33c4963bf53 Merge tag 'nfsd-6.9-5' of git://git.kernel.or..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12499380980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  e33c4963bf53

--- x/fs/namei.c
+++ y/fs/namei.c
@@ -3795,8 +3795,11 @@ static struct file *path_openat(struct n
 		while (!(error = link_path_walk(s, nd)) &&
 		       (s = open_last_lookups(nd, file, op)) != NULL)
 			;
-		if (!error)
+		if (!error) {
+			path_get(&nd->path);
 			error = do_open(nd, file, op);
+			path_put(&nd->path);
+		}
 		terminate_walk(nd);
 	}
 	if (likely(!error)) {
--