From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) (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 785D43164B4 for ; Fri, 10 Apr 2026 04:48:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.132 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775796528; cv=none; b=VjNtohmBBTZpnFaV3759MCbCkTyqpa2KRaaC5QgUjJVO3bZAwZJbyE452790Zv96owKCusyctvgnVTMG5WsvufiAecAsEpD8jpQ6voyNYxuPWAmR2kEYCVjsHtjlnPcGgPK6T1Rp031tkrRi+Ut3M6N34J4hiwudhmQwlhfOPQo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775796528; c=relaxed/simple; bh=x62Bfz6PwUwmNSTR+bUQ3GiiT5MyoRj5zIyWT3iFwUE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=buAYaORqqOYMyMKhRXhKQZWUXsmnoCmgC5O1jOOZ+s55E0XzNvSA7W3nmjknhIezCXuYBi7nrB75DF26av4+H1qW1XWS1EYoxIcQJVH+km6mKBLOFT1Dbe3xzY/bSzIHC8oGA5GS/KDiXMVBamHA+RyJQMc1vP+mIRGj9DSI4gs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=WfduGMhE; arc=none smtp.client-ip=115.124.30.132 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="WfduGMhE" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1775796515; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=McOZ6YH91rrFMXHgA8NeNn+4rHqeVrg9eBs9xVooaWo=; b=WfduGMhELRNObmzInwkZWXlrTRUWJof1Qr+gdi6Yk6vpeAzV9oKOMbqAkAZz/4ZYKbuUqHxHUMSoDLIInRIL6FwAag/hLmSznz3bbtZ8nTYq7DEKD3+VZdgI8CWJf2vrp+9YGe/z3eTLZ6SIVfHOzrsUWtgK96ZH7VWOcSV77eQ= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R111e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045098064;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0X0k4o8o_1775796514; Received: from 30.221.145.28(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0X0k4o8o_1775796514 cluster:ay36) by smtp.aliyun-inc.com; Fri, 10 Apr 2026 12:48:35 +0800 Message-ID: <6e71b245-233f-4cab-a7bc-ccf75f555f97@linux.alibaba.com> Date: Fri, 10 Apr 2026 12:48:33 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] ocfs2: validate bg_bits during freefrag scan To: Heming Zhao , ZhengYuan Huang , akpm Cc: mark@fasheh.com, jlbec@evilplan.org, ocfs2-devel@lists.linux.dev, linux-kernel@vger.kernel.org, baijiaju1990@gmail.com, r33s3n6@gmail.com, zzzccc427@gmail.com References: <20260410034220.3825769-1-gality369@gmail.com> From: Joseph Qi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/10/26 11:56 AM, Heming Zhao wrote: > On Fri, Apr 10, 2026 at 11:42:20AM +0800, ZhengYuan Huang wrote: >> [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. >> >> Fixes: d24a10b9f8ed ("Ocfs2: Add a new code 'OCFS2_INFO_FREEFRAG' for o2info ioctl.") >> Signed-off-by: ZhengYuan Huang > > LGTM. > Reviewed-by: Heming Zhao Reviewed-by: Joseph Qi > >> --- >> v5: >> - move max_bitmap_bits computation out of the group loop >> - restore the untouched blank line after assigning bg >> >> v4: >> - add the freefrag introduction commit as a Fixes tag >> - use cluster allocator bitmap sizing with ocfs2_group_bitmap_size(..., 0, ...) >> - drop the unnecessary 8U suffix and tighten the mlog() formatting >> >> v3: >> - restore the empty-group fast path before computing bitmap limits >> - move the bg_bits clamp below bg_free_bits_count to skip extra work >> for empty groups >> >> v2: >> - use ocfs2_group_bitmap_size() instead of the on-disk bg_size field >> - clamp bg_bits to the computed bitmap capacity and continue scanning >> --- >> fs/ocfs2/ioctl.c | 19 ++++++++++++++++++- >> 1 file changed, 18 insertions(+), 1 deletion(-) >> >> diff --git a/fs/ocfs2/ioctl.c b/fs/ocfs2/ioctl.c >> index b6864602814c..10f573a8b6b6 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++) { >> -- >> 2.43.0 >> >>