linux-kernel - PROBLEM: Corrupt inode flags when remove ATTR_SYS flag on fat file system mounted with “sys

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Date:	Tue, 31 May 2011 12:27:24 +0400
From:	Dmitry Dmitriev <dimondmm@...dex.ru>
To:	hirofumi@...l.parknet.co.jp, linux-kernel@...r.kernel.org
Subject: PROBLEM: Corrupt inode flags when remove ATTR_SYS flag on fat file system mounted with “sys_immutable” mount option.

Hello,

Inode flags are corrupted when removing ATTR_SYS flag by FAT_IOCTL_SET_ATTRIBUTES ioctl on fat file system mounted with “sys_immutable” mount option. In this case S_IMMUTABLE flag must be removed from inode flags, but actually removed all other flags except S_IMMUTABLE. This problem observed on 2.6.34 kernel, but it seems still exist( after examine of 2.6.39 kernel source code ).

The problem in fat_ioctl_set_attributes function( fs/fat/file.c ). This function contains following code(2.6.39 kernel):
 101        if (sbi->options.sys_immutable) {
 102                if (attr & ATTR_SYS)
 103                        inode->i_flags |= S_IMMUTABLE;
 104                else
 105                        inode->i_flags &= S_IMMUTABLE;
 106        }

Instead of removing S_IMMUTABLE flag from inode flags on line 105 function removes all other flags from inode flags. I think that line 105 must be following:

 105                        inode->i_flags &= ~S_IMMUTABLE;

Regards,
Dmitry
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