From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Date: Wed, 13 Apr 2011 07:31:52 +0000 (+0300)
Subject: UBIFS: fix oops when R/O file-system is fsync'ed
X-Git-Tag: v2.6.39-rc4~23^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=78530bf7f2559b317c04991b52217c1608d5a58d;p=pandora-kernel.git

UBIFS: fix oops when R/O file-system is fsync'ed

This patch fixes severe UBIFS bug: UBIFS oopses when we 'fsync()' an
file on R/O-mounter file-system. We (the UBIFS authors) incorrectly
thought that VFS would not propagate 'fsync()' down to the file-system
if it is read-only, but this is not the case.

It is easy to exploit this bug using the following simple perl script:

use strict;
use File::Sync qw(fsync sync);

die "File path is not specified" if not defined $ARGV[0];
my $path = $ARGV[0];

open FILE, "<", "$path" or die "Cannot open $path: $!";
fsync(\*FILE) or die "cannot fsync $path: $!";
close FILE or die "Cannot close $path: $!";

Thanks to Reuben Dowle <Reuben.Dowle@navico.com> for reporting about this
issue.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Reported-by: Reuben Dowle <Reuben.Dowle@navico.com>
Cc: stable@kernel.org
---

Reading git-diff-tree failed