From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 962D2255F28; Tue, 11 Nov 2025 01:40:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825224; cv=none; b=T3cSy3HzkY8Qp+s+FhyWxmP4uT0mCiHuqr9OL4lUvRgj//OfnlB0B6Yf29wDCY9D67XJC8YTP+swoXpN4C0idOsOV4Q38BBCd1WnoRzrsQ+lX/NX9CjxEuS0zvPVFjfYPJymlXjyGUBHQOOZZvuo9HfBcNAIoJ4bCOB5aJb6KB0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762825224; c=relaxed/simple; bh=i1feWGyNxKDtnd4mc+OnqdsCD7E1R0M8lv83oWWO4aE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=l3c76dvbaS+Tx7lV2QiT3xzcrLHbtnTJKBzDppsoKUC3gVjs5cB9+pjPdpHLwJgFe5CVLfklKyKlcJOUMLy2c4rpHOV48DSBmDBjf0GFWxMFrKw7EoIFCA/TZlQlyCu7yr4KjGIn5Bw6xCCbUUQdIAdvd/J6kkiWXtnxVqnEmGk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VeVnw/xx; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VeVnw/xx" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 33767C116B1; Tue, 11 Nov 2025 01:40:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1762825224; bh=i1feWGyNxKDtnd4mc+OnqdsCD7E1R0M8lv83oWWO4aE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VeVnw/xxlOAbO/H6wjkcE9WzmEpJ8/VJNUi2upzrCL2n9jBo9AmH1XB/jn3w/vGqp x+55YnQbT7/kOksVHVsn03r4uTVmByIYGcH5dN2nMtHSWe4L/SIKMO58st8VOOlWyD 7pmLLajAs3Hst2YfReF2tLNrI7Ui0m6SKdmblaiM= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+a725ab460fc1def9896f@syzkaller.appspotmail.com, Yuezhang Mo , Sungjong Seo , Namjae Jeon , Sasha Levin Subject: [PATCH 6.17 670/849] exfat: validate cluster allocation bits of the allocation bitmap Date: Tue, 11 Nov 2025 09:44:00 +0900 Message-ID: <20251111004552.618679163@linuxfoundation.org> X-Mailer: git-send-email 2.51.2 In-Reply-To: <20251111004536.460310036@linuxfoundation.org> References: <20251111004536.460310036@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Namjae Jeon [ Upstream commit 79c1587b6cda74deb0c86fc7ba194b92958c793c ] syzbot created an exfat image with cluster bits not set for the allocation bitmap. exfat-fs reads and uses the allocation bitmap without checking this. The problem is that if the start cluster of the allocation bitmap is 6, cluster 6 can be allocated when creating a directory with mkdir. exfat zeros out this cluster in exfat_mkdir, which can delete existing entries. This can reallocate the allocated entries. In addition, the allocation bitmap is also zeroed out, so cluster 6 can be reallocated. This patch adds exfat_test_bitmap_range to validate that clusters used for the allocation bitmap are correctly marked as in-use. Reported-by: syzbot+a725ab460fc1def9896f@syzkaller.appspotmail.com Tested-by: syzbot+a725ab460fc1def9896f@syzkaller.appspotmail.com Reviewed-by: Yuezhang Mo Reviewed-by: Sungjong Seo Signed-off-by: Namjae Jeon Signed-off-by: Sasha Levin --- fs/exfat/balloc.c | 72 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 60 insertions(+), 12 deletions(-) diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c index cc01556c9d9b3..071448adbd5d9 100644 --- a/fs/exfat/balloc.c +++ b/fs/exfat/balloc.c @@ -26,12 +26,55 @@ /* * Allocation Bitmap Management Functions */ +static bool exfat_test_bitmap_range(struct super_block *sb, unsigned int clu, + unsigned int count) +{ + struct exfat_sb_info *sbi = EXFAT_SB(sb); + unsigned int start = clu; + unsigned int end = clu + count; + unsigned int ent_idx, i, b; + unsigned int bit_offset, bits_to_check; + __le_long *bitmap_le; + unsigned long mask, word; + + if (!is_valid_cluster(sbi, start) || !is_valid_cluster(sbi, end - 1)) + return false; + + while (start < end) { + ent_idx = CLUSTER_TO_BITMAP_ENT(start); + i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx); + b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx); + + bitmap_le = (__le_long *)sbi->vol_amap[i]->b_data; + + /* Calculate how many bits we can check in the current word */ + bit_offset = b % BITS_PER_LONG; + bits_to_check = min(end - start, + (unsigned int)(BITS_PER_LONG - bit_offset)); + + /* Create a bitmask for the range of bits to check */ + if (bits_to_check >= BITS_PER_LONG) + mask = ~0UL; + else + mask = ((1UL << bits_to_check) - 1) << bit_offset; + word = lel_to_cpu(bitmap_le[b / BITS_PER_LONG]); + + /* Check if all bits in the mask are set */ + if ((word & mask) != mask) + return false; + + start += bits_to_check; + } + + return true; +} + static int exfat_allocate_bitmap(struct super_block *sb, struct exfat_dentry *ep) { struct exfat_sb_info *sbi = EXFAT_SB(sb); long long map_size; - unsigned int i, need_map_size; + unsigned int i, j, need_map_size; sector_t sector; sbi->map_clu = le32_to_cpu(ep->dentry.bitmap.start_clu); @@ -58,20 +101,25 @@ static int exfat_allocate_bitmap(struct super_block *sb, sector = exfat_cluster_to_sector(sbi, sbi->map_clu); for (i = 0; i < sbi->map_sectors; i++) { sbi->vol_amap[i] = sb_bread(sb, sector + i); - if (!sbi->vol_amap[i]) { - /* release all buffers and free vol_amap */ - int j = 0; - - while (j < i) - brelse(sbi->vol_amap[j++]); - - kvfree(sbi->vol_amap); - sbi->vol_amap = NULL; - return -EIO; - } + if (!sbi->vol_amap[i]) + goto err_out; } + if (exfat_test_bitmap_range(sb, sbi->map_clu, + EXFAT_B_TO_CLU_ROUND_UP(map_size, sbi)) == false) + goto err_out; + return 0; + +err_out: + j = 0; + /* release all buffers and free vol_amap */ + while (j < i) + brelse(sbi->vol_amap[j++]); + + kvfree(sbi->vol_amap); + sbi->vol_amap = NULL; + return -EIO; } int exfat_load_bitmap(struct super_block *sb) -- 2.51.0