linux-kernel - Re: [syzbot] [overlayfs?] possible deadlock in seq_read

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Date: Sat, 27 Jan 2024 19:46:10 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+da4f9f61f96525c62cc7@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [overlayfs?] possible deadlock in seq_read_iter (2)

On Tue, 19 Dec 2023 11:43:27 -0800
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    2cf4f94d8e86 Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=154aa8d6e80000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  2cf4f94d8e86

--- x/fs/namei.c
+++ y/fs/namei.c
@@ -3533,6 +3533,8 @@ static const char *open_last_lookups(str
 
 	if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
 		got_write = !mnt_want_write(nd->path.mnt);
+		if (!got_write && (open_flag & O_CREAT))
+			return ERR_PTR(-EISDIR);
 		/*
 		 * do _not_ fail yet - we might not need that or fail with
 		 * a different error; let lookup_open() decide; we'll be
--