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 8EE4E3D904D; Wed, 8 Apr 2026 18:19:58 +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=1775672398; cv=none; b=KTJ4ZbZ6GS/47FQjIzLX6b4CqPPAj5jLEKT0YSQCs6cJkHn0crjRUVDveolWxB6+jJaRNK670W9LVPd0RtddX+OWs9pBOYglw6vDae8Nw6rSAoSsUvrcqgfRL0HD1jvmVO9Xn4L2+tLq/VjVaOFM9f3lCvSSfWFnH+O5c+atxN4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775672398; c=relaxed/simple; bh=ommKtNWEmQalCKhwYztBHafVqzqtJAp+L5VItLnVGLs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tp69JZ6f+pv0vg7BSvqi+3XmnTP0rIBvf3O1kMpsxOjlQuoGixsnISUl17dwC3HE6xw2xDXobY12vd6dLjLXGD6PpcmzQWCyIPLVjDD0fSvdejAzo7jlpM2hipI8+b0Sd+x9EmYbnEWya+WQImW98nNwYBKgmxRowCgwGFx4EN8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TvASjKh/; 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="TvASjKh/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D9517C19425; Wed, 8 Apr 2026 18:19:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1775672398; bh=ommKtNWEmQalCKhwYztBHafVqzqtJAp+L5VItLnVGLs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TvASjKh/vPSCYvWHm+P4aj6sGHhQikaaCarlrdIeY21Xd0sKTzkD42p/W+w4we/U/ AyAabCtqbXL2AC7aUzo1WCLW0evhxfj4Ni9Ye2GXkFp/qCdiqD/wA79/wWEI7p6X8l 4LzA9fqADoeCQSDuONiMS1DKUmv2YFalRikZbNkk= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+4fc98ed414ae63d1ada2@syzkaller.appspotmail.com, syzbot+de04e06b28cfecf2281c@syzkaller.appspotmail.com, syzbot+c8c8238b394be4a1087d@syzkaller.appspotmail.com, Alexey Panov , Gao Xiang Subject: [PATCH 6.1 297/312] erofs: handle overlapped pclusters out of crafted images properly Date: Wed, 8 Apr 2026 20:03:34 +0200 Message-ID: <20260408175944.858445194@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260408175933.715315542@linuxfoundation.org> References: <20260408175933.715315542@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gao Xiang 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 Signed-off-by: Greg Kroah-Hartman --- fs/erofs/zdata.c | 60 +++++++++++++++++++++++++++++-------------------------- 1 file changed, 32 insertions(+), 28 deletions(-) --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -1331,14 +1331,14 @@ repeat: 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 @@ -1352,22 +1352,24 @@ repeat: 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: @@ -1520,16 +1522,11 @@ static void z_erofs_submit_queue(struct 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); @@ -1538,6 +1535,13 @@ submit_bio_retry: 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; @@ -1558,7 +1562,7 @@ submit_bio_retry: } if (bio_add_page(bio, page, PAGE_SIZE, 0) < PAGE_SIZE) - goto submit_bio_retry; + goto drain_io; last_index = cur; bypass = false;