From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id A000410BA420 for ; Fri, 27 Mar 2026 04:33:29 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4fhnnz72J8z2xR4; Fri, 27 Mar 2026 15:33:27 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=115.124.30.101 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1774586007; cv=none; b=TN/WxVFKmGhd0WHFIDpYVj5jwi3/F5uN+J1VTGmvEM5T7d5UBoH2c9IR7Dq0oLZyFAK9mmh5irAaNRp0yODO29MQzwBsA4jyaxbYBY2HqEVlqGLhVNB9JZxu7Sar7NUG1dMEkE4KUXg5otiQWcI1ji/skqLddiZyMmfDmLUVoFpCaqxj/6Vay3C6B9CdXfkHKwBbTTS8aJF3cNi4PFZ/XQhZhSGLHqDzCrHiV4xbdtkVWcKyFhxB/sIZ0dnnOk+2w1THu6jMKPMoLhQRSfJYGZvP+pb16ibNJ4Y6ABm0SVLg6yeJeieDKZ87jVAPfKvBb2soO83gkHaBKogaAA1muA== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1774586007; c=relaxed/relaxed; bh=qD5WGzY9SirQ9xlNJVoQqH4Rcm41JAwbu6EYRLwDR08=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bYUo6DhIEpxpYZhSsBTcZO1/r5bac4v7QavGQlADytdGKWf0CMz3hSNYZwmO3jSdwH/6PRpCrDdkawLlzFEeHWaRDUfsJKrDLVE0CkHiwgmswxjy3aWwbR+DTpneXEDBNDCN0xQ+DVd2xGSLtrS6U1yJAvbZseiEg1xuCIADuQ1zY58cBICK35GgyLat9ldPEWImjWiSxXpHr+HvOfrl5Q1PahVGzXSvjG5NNz7kurTcm+rkTTNbJ1PLcPt8Hgtl+6kYl712Fcx4RIHHq+cSzeOsd1wtv282lbSJci1SFkcI2cpeSeFtMx1QboaWineiSogmX4rWajSOSYRmeaucHg== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; dkim=pass (1024-bit key; unprotected) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=o8FlPOUh; dkim-atps=neutral; spf=pass (client-ip=115.124.30.101; helo=out30-101.freemail.mail.aliyun.com; envelope-from=hsiangkao@linux.alibaba.com; receiver=lists.ozlabs.org) smtp.mailfrom=linux.alibaba.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.a=rsa-sha256 header.s=default header.b=o8FlPOUh; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=linux.alibaba.com (client-ip=115.124.30.101; helo=out30-101.freemail.mail.aliyun.com; envelope-from=hsiangkao@linux.alibaba.com; receiver=lists.ozlabs.org) Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4fhnnx5BFVz2xHX for ; Fri, 27 Mar 2026 15:33:24 +1100 (AEDT) DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1774586000; h=From:To:Subject:Date:Message-ID:MIME-Version; bh=qD5WGzY9SirQ9xlNJVoQqH4Rcm41JAwbu6EYRLwDR08=; b=o8FlPOUhj1/J9r/C/F9EyLyGWACp4S7LeQWVXu/RndYcVzPzmt3Ay2vmpbprLP3qq2uX/PtOAdORwkPtDztDRrzzXHSp3Lqzmxrqdod068sXl07fZYVSg9p+Z4GzHWLy5Ij+lxuBiQbz0cUrSj1qtk/34HutMEmVyrQNHJIWLOM= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037026112;MF=hsiangkao@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0X.mwfTV_1774585993; Received: from x31i01179.sqa.na131.tbsite.net(mailfrom:hsiangkao@linux.alibaba.com fp:SMTPD_---0X.mwfTV_1774585993 cluster:ay36) by smtp.aliyun-inc.com; Fri, 27 Mar 2026 12:33:18 +0800 From: Gao Xiang To: stable@vger.kernel.org, Greg Kroah-Hartman Cc: linux-erofs@lists.ozlabs.org, Gao Xiang , syzbot+4fc98ed414ae63d1ada2@syzkaller.appspotmail.com, syzbot+de04e06b28cfecf2281c@syzkaller.appspotmail.com, syzbot+c8c8238b394be4a1087d@syzkaller.appspotmail.com, Alexey Panov Subject: [PATCH 6.1.y 1/2] erofs: handle overlapped pclusters out of crafted images properly Date: Fri, 27 Mar 2026 12:33:12 +0800 Message-ID: <20260327043312.1118901-1-hsiangkao@linux.alibaba.com> X-Mailer: git-send-email 2.43.5 X-Mailing-List: linux-erofs@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit commit 9e2f9d34dd12e6e5b244ec488bcebd0c2d566c50 upstream. syzbot reported a task hang issue due to a deadlock case where it is waiting for the folio lock of a cached folio that will be used for cache I/Os. After looking into the crafted fuzzed image, I found it's formed with several overlapped big pclusters as below: Ext: logical offset | length : physical offset | length 0: 0.. 16384 | 16384 : 151552.. 167936 | 16384 1: 16384.. 32768 | 16384 : 155648.. 172032 | 16384 2: 32768.. 49152 | 16384 : 537223168.. 537239552 | 16384 ... Here, extent 0/1 are physically overlapped although it's entirely _impossible_ for normal filesystem images generated by mkfs. First, managed folios containing compressed data will be marked as up-to-date and then unlocked immediately (unlike in-place folios) when compressed I/Os are complete. If physical blocks are not submitted in the incremental order, there should be separate BIOs to avoid dependency issues. However, the current code mis-arranges z_erofs_fill_bio_vec() and BIO submission which causes unexpected BIO waits. Second, managed folios will be connected to their own pclusters for efficient inter-queries. However, this is somewhat hard to implement easily if overlapped big pclusters exist. Again, these only appear in fuzzed images so let's simply fall back to temporary short-lived pages for correctness. Additionally, it justifies that referenced managed folios cannot be truncated for now and reverts part of commit 2080ca1ed3e4 ("erofs: tidy up `struct z_erofs_bvec`") for simplicity although it shouldn't be any difference. [Alexey: This patch follows linux 6.6.y conflict resolution changes of struct folio -> struct page] Reported-by: syzbot+4fc98ed414ae63d1ada2@syzkaller.appspotmail.com Reported-by: syzbot+de04e06b28cfecf2281c@syzkaller.appspotmail.com Reported-by: syzbot+c8c8238b394be4a1087d@syzkaller.appspotmail.com Tested-by: syzbot+4fc98ed414ae63d1ada2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/r/0000000000002fda01061e334873@google.com Fixes: 8e6c8fa9f2e9 ("erofs: enable big pcluster feature") Link: https://lore.kernel.org/r/20240910070847.3356592-1-hsiangkao@linux.alibaba.com Signed-off-by: Alexey Panov Link: https://lore.kernel.org/r/20250304110558.8315-2-apanov@astralinux.ru Link: https://lore.kernel.org/r/20250304110558.8315-1-apanov@astralinux.ru [ Gao Xiang: re-address the previous Alexey's backport. ] CVE: CVE-2024-47736 Signed-off-by: Gao Xiang --- fs/erofs/zdata.c | 60 ++++++++++++++++++++++++++---------------------- 1 file changed, 32 insertions(+), 28 deletions(-) diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 5e6580217318..aa311aed0dd8 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -1328,14 +1328,14 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl, goto out; lock_page(page); - - /* only true if page reclaim goes wrong, should never happen */ - DBG_BUGON(justfound && PagePrivate(page)); - - /* the page is still in manage cache */ - if (page->mapping == mc) { + if (likely(page->mapping == mc)) { WRITE_ONCE(pcl->compressed_bvecs[nr].page, page); + oldpage = page; + /* + * The cached folio is still in managed cache but without + * a valid `->private` pcluster hint. Let's reconnect them. + */ if (!PagePrivate(page)) { /* * impossible to be !PagePrivate(page) for @@ -1349,22 +1349,24 @@ static struct page *pickup_page_for_submission(struct z_erofs_pcluster *pcl, SetPagePrivate(page); } - /* no need to submit io if it is already up-to-date */ - if (PageUptodate(page)) { - unlock_page(page); - page = NULL; + if (likely(page->private == (unsigned long)pcl)) { + /* don't submit cache I/Os again if already uptodate */ + if (PageUptodate(page)) { + unlock_page(page); + page = NULL; + + } + goto out; } - goto out; + /* + * Already linked with another pcluster, which only appears in + * crafted images by fuzzers for now. But handle this anyway. + */ + tocache = false; /* use temporary short-lived pages */ + } else { + DBG_BUGON(1); /* referenced managed folios can't be truncated */ + tocache = true; } - - /* - * the managed page has been truncated, it's unsafe to - * reuse this one, let's allocate a new cache-managed page. - */ - DBG_BUGON(page->mapping); - DBG_BUGON(!justfound); - - tocache = true; unlock_page(page); put_page(page); out_allocpage: @@ -1517,16 +1519,11 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f, end = cur + pcl->pclusterpages; do { - struct page *page; - - page = pickup_page_for_submission(pcl, i++, - &f->pagepool, mc); - if (!page) - continue; + struct page *page = NULL; if (bio && (cur != last_index + 1 || last_bdev != mdev.m_bdev)) { -submit_bio_retry: +drain_io: submit_bio(bio); if (memstall) { psi_memstall_leave(&pflags); @@ -1535,6 +1532,13 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f, bio = NULL; } + if (!page) { + page = pickup_page_for_submission(pcl, i++, + &f->pagepool, mc); + if (!page) + continue; + } + if (unlikely(PageWorkingset(page)) && !memstall) { psi_memstall_enter(&pflags); memstall = 1; @@ -1555,7 +1559,7 @@ static void z_erofs_submit_queue(struct z_erofs_decompress_frontend *f, } if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) - goto submit_bio_retry; + goto drain_io; last_index = cur; bypass = false; -- 2.43.5