From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755837Ab3FDOVM (ORCPT ); Tue, 4 Jun 2013 10:21:12 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:46748 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755713Ab3FDOIE (ORCPT ); Tue, 4 Jun 2013 10:08:04 -0400 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: OGAWA Hirofumi , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 28/70] fat: fix possible overflow for fat_clusters Date: Tue, 4 Jun 2013 15:06:44 +0100 Message-Id: <1370354846-14213-29-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 1.8.1.2 In-Reply-To: <1370354846-14213-1-git-send-email-luis.henriques@canonical.com> References: <1370354846-14213-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.14 -stable review patch. If anyone has any objections, please let me know. ------------------ From: OGAWA Hirofumi commit 7b92d03c3239f43e5b86c9cc9630f026d36ee995 upstream. Intermediate value of fat_clusters can be overflowed on 32bits arch. Reported-by: Krzysztof Strasburger Signed-off-by: OGAWA Hirofumi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds [ luis: adjust context ] Signed-off-by: Luis Henriques --- fs/fat/inode.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 0038b32..e69b441e 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -1218,6 +1218,19 @@ static int fat_read_root(struct inode *inode) return 0; } +static unsigned long calc_fat_clusters(struct super_block *sb) +{ + struct msdos_sb_info *sbi = MSDOS_SB(sb); + + /* Divide first to avoid overflow */ + if (sbi->fat_bits != 12) { + unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits; + return ent_per_sec * sbi->fat_length; + } + + return sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits; +} + /* * Read the super block of an MS-DOS FS. */ @@ -1415,7 +1428,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12; /* check that FAT table does not overflow */ - fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits; + fat_clusters = calc_fat_clusters(sb); total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT); if (total_clusters > MAX_FAT(sb)) { if (!silent) -- 1.8.1.2