linux-kernel - CIFS kernel module bug

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Date:	Fri, 30 Sep 2011 14:58:58 +0100
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	Steve French <sfrench@...ba.org>
Cc:	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	LKML <linux-kernel@...r.kernel.org>,
	PWF Linux <pwf-linux@....cam.ac.uk>
Subject: CIFS  kernel module bug

Hi,

Looking at the current kernel (in Linus' repository on github) there is a silly logic bug in the cifs module in fs/cifs/cifsfs.c::cifs_llseek() there is this bit of code:

	/*
	 * origin == SEEK_END || SEEK_DATA || SEEK_HOLE => we must revalidate
	 * the cached file length
	 */
	if (origin != SEEK_SET || origin != SEEK_CUR) {

The logical or should be a logical and, i.e. this should be:

	if (origin != SEEK_SET && origin != SEEK_CUR) {

As the code is at present that line is ALWAYS true because origin is ALWAYS either != SEEK_SET or != SEEK_CUR as if it equals one it cannot equal the other and vice versa…

So at the moment it always does the revalidation instead of only for SEEK_END, SEEK_DATA, and SEEK_HOLE.

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/

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