linux-kernel - Re: [syzbot] [overlayfs?] WARNING in shmem

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Message-ID: <20250816054208.4763-1-hdanton@sina.com>
Date: Sat, 16 Aug 2025 13:42:07 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+ec9fab8b7f0386b98a17@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [overlayfs?] WARNING in shmem_unlink

> Date: Fri, 15 Aug 2025 20:08:33 -0700	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    0cc53520e68b Merge tag 'probes-fixes-v6.17-rc1' of git://g..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14a003a2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=13f39c6a0380a209
> dashboard link: https://syzkaller.appspot.com/bug?extid=ec9fab8b7f0386b98a17
> compiler:       Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1387bc34580000

#syz test

--- x/fs/overlayfs/super.c
+++ y/fs/overlayfs/super.c
@@ -695,7 +695,7 @@ static int ovl_make_workdir(struct super
 	tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
 	ofs->tmpfile = !IS_ERR(tmpfile);
 	if (ofs->tmpfile)
-		fput(tmpfile);
+		;
 	else
 		pr_warn("upper fs does not support tmpfile.\n");
 
@@ -790,6 +790,8 @@ static int ovl_make_workdir(struct super
 	}
 out:
 	mnt_drop_write(mnt);
+	if (ofs->tmpfile)
+		fput(tmpfile);
 	return err;
 }
 
--