From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 053B13D75D3; Wed, 20 May 2026 17:37:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779298634; cv=none; b=QyAZJmgryjJrR8LPKHWeYKqZpp8H3N4GCPpZZmuG6dxGvRXvVsBTQhsIqQNL6WCz9+QT9qgypL1z+LFPInJqqsXq4wxAYjZh1RgtksR/+nyrBAOvOhlpywC7EW/VUhhQOaBIRILbzrO6LD927dlcBglGkLvgs8YANVmp+/SGN88= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779298634; c=relaxed/simple; bh=TXs0R0Y0JKI7aAMGAKCCiqNhXxcg/nAvOLeuH4GeBu8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NIFzouCXeFQvlwzBpXrM/HmkNs7iKGjGiCQo30BaE3IeMBvpJVuegSv4BtxUo7i3mZiGzmQmmGtkMrMKA7WHGVpWCJghz6F2hZAx5X0K8pKvzUOgwsB2QqElBxNqew+fIqJx3+RLv8i38CTwbpoAYY2N/TTIr3UNERZLn5Z7j6Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=nFmu5dJG; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="nFmu5dJG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 747171F000E9; Wed, 20 May 2026 17:37:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1779298632; bh=Vi3ExwNN7L8XWcxQ4Q45amVLjpnLP3qnT8l2/2s6qFc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nFmu5dJGwraG3jXRWZfZ2rtIb7LSumv2dSOAimHUiEAc0QNRu6WTGrDXdOw2i0no9 Eaz9ZCyehVN8ucBqbSRcdTWlMhrYouJW1TudKdMOwxq4rWCJ5pUGfs2o3n9mW1u6P6 wS3ZM4tn5WD2i6ZUSu1G4NneVl1vm7jn3/zG2WyQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, ZhengYuan Huang , Heming Zhao , Joseph Qi , Mark Fasheh , Joel Becker , Junxiao Bi , Changwei Ge , Jun Piao , Andrew Morton , Sasha Levin Subject: [PATCH 6.18 444/957] ocfs2: validate bg_bits during freefrag scan Date: Wed, 20 May 2026 18:15:27 +0200 Message-ID: <20260520162144.149983291@linuxfoundation.org> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260520162134.554764788@linuxfoundation.org> References: <20260520162134.554764788@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 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: ZhengYuan Huang [ Upstream commit 8f687eeed3da3012152b0f9473f578869de0cd7b ] [BUG] A crafted filesystem can trigger an out-of-bounds bitmap walk when OCFS2_IOC_INFO is issued with OCFS2_INFO_FL_NON_COHERENT. BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: use-after-free in test_bit_le include/asm-generic/bitops/le.h:21 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 Read of size 8 at addr ffff888031bce000 by task syz.0.636/1435 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xbe/0x130 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xd1/0x650 mm/kasan/report.c:482 kasan_report+0xfb/0x140 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 [inline] kasan_check_range+0x11c/0x200 mm/kasan/generic.c:200 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 instrument_atomic_read include/linux/instrumented.h:68 [inline] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] test_bit_le include/asm-generic/bitops/le.h:21 [inline] ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 ocfs2_info_handle+0x18d/0x2a0 fs/ocfs2/ioctl.c:828 ocfs2_ioctl+0x632/0x6e0 fs/ocfs2/ioctl.c:913 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x197/0x1e0 fs/ioctl.c:583 ... [CAUSE] ocfs2_info_freefrag_scan_chain() uses on-disk bg_bits directly as the bitmap scan limit. The coherent path reads group descriptors through ocfs2_read_group_descriptor(), which validates the descriptor before use. The non-coherent path uses ocfs2_read_blocks_sync() instead and skips that validation, so an impossible bg_bits value can drive the bitmap walk past the end of the block. [FIX] Compute the bitmap capacity from the filesystem format with ocfs2_group_bitmap_size(), report descriptors whose bg_bits exceeds that limit, and clamp the scan to the computed capacity. This keeps the freefrag report going while avoiding reads beyond the buffer. Link: https://lkml.kernel.org/r/20260410034220.3825769-1-gality369@gmail.com Fixes: d24a10b9f8ed ("Ocfs2: Add a new code 'OCFS2_INFO_FREEFRAG' for o2info ioctl.") Signed-off-by: ZhengYuan Huang Reviewed-by: Heming Zhao Reviewed-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Junxiao Bi Cc: Changwei Ge Cc: Jun Piao Cc: Heming Zhao Signed-off-by: Andrew Morton Signed-off-by: Sasha Levin --- fs/ocfs2/ioctl.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c index b6864602814c4..b004e7117a5f3 100644 --- a/fs/ocfs2/ioctl.c +++ b/fs/ocfs2/ioctl.c @@ -441,13 +441,16 @@ static int ocfs2_info_freefrag_scan_chain(struct ocfs2_super *osb, struct buffer_head *bh = NULL; struct ocfs2_group_desc *bg = NULL; - unsigned int max_bits, num_clusters; + unsigned int max_bits, max_bitmap_bits, num_clusters; unsigned int offset = 0, cluster, chunk; unsigned int chunk_free, last_chunksize = 0; if (!le32_to_cpu(rec->c_free)) goto bail; + max_bitmap_bits = 8 * ocfs2_group_bitmap_size(osb->sb, 0, + osb->s_feature_incompat); + do { if (!bg) blkno = le64_to_cpu(rec->c_blkno); @@ -479,6 +482,19 @@ static int ocfs2_info_freefrag_scan_chain(struct ocfs2_super *osb, continue; max_bits = le16_to_cpu(bg->bg_bits); + + /* + * Non-coherent scans read raw blocks and do not get the + * bg_bits validation from + * ocfs2_read_group_descriptor(). + */ + if (max_bits > max_bitmap_bits) { + mlog(ML_ERROR, + "Group desc #%llu has %u bits, max bitmap bits %u\n", + (unsigned long long)blkno, max_bits, max_bitmap_bits); + max_bits = max_bitmap_bits; + } + offset = 0; for (chunk = 0; chunk < chunks_in_group; chunk++) { -- 2.53.0