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    Subject[10/26] UBIFS: fix oops when R/O file-system is fsynced
    2.6.33-longterm review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

    commit 78530bf7f2559b317c04991b52217c1608d5a58d upstream.

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    fs/ubifs/file.c | 3 +++
    1 file changed, 3 insertions(+)

    --- a/fs/ubifs/file.c
    +++ b/fs/ubifs/file.c
    @@ -1311,6 +1311,9 @@ int ubifs_fsync(struct file *file, struc

    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.



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