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

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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
This commit is contained in:
Artem Bityutskiy 2011-04-13 10:31:52 +03:00
parent a6360dd37e
commit 78530bf7f2
1 changed files with 3 additions and 0 deletions
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3
fs/ubifs/file.c
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@ -1312,6 +1312,9 @@ int ubifs_fsync(struct file *file, int datasync)
dbg_gen("syncing inode %lu", inode->i_ino);
if (inode->i_sb->s_flags & MS_RDONLY)
return 0;
/*
* VFS has already synchronized dirty pages for this inode. Synchronize
* the inode unless this is a 'datasync()' call.