linux-kernel - NFS infinite loop in filemap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <E1JtqLW-0005j5-KU@pomaz-ex.szeredi.hu>
Date:	Wed, 07 May 2008 22:34:38 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	trond.myklebust@....uio.no, npiggin@...e.de
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: NFS infinite loop in filemap_fault()

Page fault on NFS apparently goes into an infinite loop if the read on
the server fails.

I don't understand the NFS readpage code, but the filemap_fault() code
looks somewhat suspicious:

	/*
	 * Umm, take care of errors if the page isn't up-to-date.
	 * Try to re-read it _once_. We do this synchronously,
	 * because there really aren't any performance issues here
	 * and we need to check for errors.
	 */
	ClearPageError(page);
	error = mapping->a_ops->readpage(file, page);
	page_cache_release(page);

	if (!error || error == AOP_TRUNCATED_PAGE)
		goto retry_find;

The comment doesn't seem to match what the it actually does: if
->readpage() is asynchronous, then this will just repeat everything,
without any guarantee that it will re-read once.

What am I missing?

Miklos
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/