linux-kernel - Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE

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Date:   Thu, 18 Oct 2018 21:58:07 +0100
From:   David Howells <dhowells@...hat.com>
To:     unlisted-recipients:; (no To-header on input)
Cc:     dhowells@...hat.com,
        Alan Jenkins <alan.christopher.jenkins@...il.com>,
        viro@...iv.linux.org.uk, torvalds@...ux-foundation.org,
        ebiederm@...ssion.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, mszeredi@...hat.com
Subject: Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE [ver #12]

David Howells <dhowells@...hat.com> wrote:

> but this fails on your modified test-fsmount with:
>
> 	shell-init: error retrieving current directory: getcwd: cannot access
> 	parent directories: No such file or directory

Actually, it doesn't fail at this point, and I do see a splat later in
fsnotify_first_mark().

	static struct fsnotify_mark *fsnotify_first_mark(struct fsnotify_mark_connector **connp)
	{
		struct fsnotify_mark_connector *conn;
		struct hlist_node *node = NULL;

		conn = srcu_dereference(*connp, &fsnotify_mark_srcu);

conn here is 6b6b6b6b6b6b6b6b.

	RIP: 0010:fsnotify_first_mark+0x5f/0xbb

	Call Trace:
	 fsnotify+0x115/0x344
	 ? __fput+0xac/0x1c1
	 __fput+0xac/0x1c1
	 task_work_run+0x78/0x9f
	 do_exit+0x525/0xa05
	 do_group_exit+0xb2/0xb2
	 __x64_sys_exit_group+0x14/0x14
	 do_syscall_64+0x7d/0x1a0
	 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The line in fsnotify is:

			fsnotify_first_mark(&mnt->mnt_fsnotify_marks);

and fsnotify() is called from fsnotify_close().

David