From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-101.freemail.mail.aliyun.com (out30-101.freemail.mail.aliyun.com [115.124.30.101]) (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 8BCB93B4EA9 for ; Wed, 1 Apr 2026 08:29:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.101 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775032197; cv=none; b=lBgfA5ILa18kZIMaFj8gO+1XRAHCWQcCZl5ZG4xEJsvXMACGcKRZ+LLwV6hv4zZbpMn90L2JpH+nXofMTa7CPrvrU+0VhR/zciQ6NNLxae6to9NZ/Wiz+QXyzeCau20u6XRFW1W9RyFIc0plJBqpAOnwSw85H4a+8dkqxEQXBIE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775032197; c=relaxed/simple; bh=hGjhSI+hvL5yY+Oja3VgTB50GBh4p+WeF5/zIgMy5NU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GbtYl9khp/whz2SXeDttukWmHe/fNeAoMWzKltvvJWJzlA6EfE4Xa9SXB9AiqN892cXnn5+nDcgv/V+Zdx6aQ3ZRYx6DGzq3RQ/Op4rS8dXMiHOXPEW7jYdvx7Tl0CGbC+CFYJY9VtLlXdDDI93Jq+OZpScXxz9qLlbpMoBdVgY= 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=Ut8C6ou9; arc=none smtp.client-ip=115.124.30.101 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="Ut8C6ou9" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1775032185; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=xIFIDn0DuXbNZzctfi/bELfZi29mvfKXWvUdlj+0FcI=; b=Ut8C6ou95qjXnqK5Fnfn/TYKU2O7VdNj9EN16rMoPNoMHA8QXmV69kAU4HAO49UxcM0iCkTaprcsrc7X4v49NmTWaOfdl5/XOf4BcnPJPjp6VcLom7tykjxO25g69vWO3omllCtgpuON9Vb+hNXssITI968bc29O745lFZljs4w= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R181e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045133197;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0X09bv4m_1775032184; Received: from 30.221.145.27(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0X09bv4m_1775032184 cluster:ay36) by smtp.aliyun-inc.com; Wed, 01 Apr 2026 16:29:45 +0800 Message-ID: <46416617-8956-4e60-8e38-2d3337adef64@linux.alibaba.com> Date: Wed, 1 Apr 2026 16:29:43 +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 v2] ocfs2: fix use-after-free in ocfs2_fault() when VM_FAULT_RETRY To: tejas bharambe Cc: "mark@fasheh.com" , "jlbec@evilplan.org" , "linux-kernel@vger.kernel.org" , "syzbot+a49010a0e8fcdeea075f@syzkaller.appspotmail.com" , "ocfs2-devel@lists.linux.dev" References: From: Joseph Qi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 4/1/26 12:20 PM, tejas bharambe wrote: > filemap_fault() may drop the mmap_lock before returning VM_FAULT_RETRY, > as documented in mm/filemap.c: > > "If our return value has VM_FAULT_RETRY set, it's because the mmap_lock > may be dropped before doing I/O or by lock_folio_maybe_drop_mmap()." > > When this happens, a concurrent munmap() can call remove_vma() and free > the vm_area_struct via RCU. The saved 'vma' pointer in ocfs2_fault() then > becomes a dangling pointer, and the subsequent trace_ocfs2_fault() call > dereferences it -- a use-after-free. > > Fix this by saving the inode reference before calling filemap_fault(), > and removing vma from the trace event. The inode remains valid across > the lock drop since the file is still open, so the trace can fire in > all cases without dereferencing the potentially freed vma. > > Reported-by: syzbot+a49010a0e8fcdeea075f@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=a49010a0e8fcdeea075f > Suggested-by: Joseph Qi > Signed-off-by: Tejas Bharambe > --- > fs/ocfs2/mmap.c | 4 ++-- > fs/ocfs2/ocfs2_trace.h | 10 ++++------ > 2 files changed, 6 insertions(+), 8 deletions(-) > > diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c > index 50e2faf64c..7a4be91d6a 100644 > --- a/fs/ocfs2/mmap.c > +++ b/fs/ocfs2/mmap.c > @@ -38,8 +38,8 @@ static vm_fault_t ocfs2_fault(struct vm_fault *vmf) > ret = filemap_fault(vmf); > ocfs2_unblock_signals(&oldset); > > - trace_ocfs2_fault(OCFS2_I(vma->vm_file->f_mapping->host)->ip_blkno, > - vma, vmf->page, vmf->pgoff); > + trace_ocfs2_fault(OCFS2_I(inode)->ip_blkno, It seems you've missed defining 'inode' at first. Joseph > + vmf->page, vmf->pgoff); > return ret; > } > > diff --git a/fs/ocfs2/ocfs2_trace.h b/fs/ocfs2/ocfs2_trace.h > index 4b32fb5658..6c2c97a980 100644 > --- a/fs/ocfs2/ocfs2_trace.h > +++ b/fs/ocfs2/ocfs2_trace.h > @@ -1246,22 +1246,20 @@ TRACE_EVENT(ocfs2_write_end_inline, > > TRACE_EVENT(ocfs2_fault, > TP_PROTO(unsigned long long ino, > - void *area, void *page, unsigned long pgoff), > - TP_ARGS(ino, area, page, pgoff), > + void *page, unsigned long pgoff), > + TP_ARGS(ino, page, pgoff), > TP_STRUCT__entry( > __field(unsigned long long, ino) > - __field(void *, area) > __field(void *, page) > __field(unsigned long, pgoff) > ), > TP_fast_assign( > __entry->ino = ino; > - __entry->area = area; > __entry->page = page; > __entry->pgoff = pgoff; > ), > - TP_printk("%llu %p %p %lu", > - __entry->ino, __entry->area, __entry->page, __entry->pgoff) > + TP_printk("%llu %p %lu", > + __entry->ino, __entry->page, __entry->pgoff) > ); > > /* End of trace events for fs/ocfs2/mmap.c. */