From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-119.freemail.mail.aliyun.com (out30-119.freemail.mail.aliyun.com [115.124.30.119]) (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 BB95F287263 for ; Thu, 2 Apr 2026 03:32:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.119 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775100758; cv=none; b=jmiS781SiNso4856Wqhlk2H/ezN/Wkmet5j2CU6/k3m5hz0fOEB3kRZIULi1RMTqklZ9wZn4sa6EQoE9G4J0y/SnkPgVIFdpfc1Uudri7XsbwGeRaLMJZD+MiZwDRQwpkDgKE3aBHXcby6zjl+QNafP+BzMbcBS5J3MkiZVGOPA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775100758; c=relaxed/simple; bh=a5+LTNgi9SF6V3+WYt8pBmlA/+4lzfs/jlyRot70miw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=l+rYfwmOXicFzVL6cRPAiOdK0CIWhoHn3En681PSqFVAjRz83u2A+FqRvqzT1ATCfG0pubYdGvgaujdi9dYnuF+Hpdaxcjda3ME3qZUVnSnOe1TeGEYfm9Vm5KoxRm08Gp7FMw7Qq0ncirMjxFZ8poQJOWIalakabXj1qRjYqmg= 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=wgFLGhp/; arc=none smtp.client-ip=115.124.30.119 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="wgFLGhp/" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1775100747; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=puBaTayvDqxUGG5DuWoaou08x+t9vvFx+Z5qWssasnM=; b=wgFLGhp/wEmPWJBzZYVPl7Z2HjV6qeG1hxZlJrHCZuvhpVSGl1dm6jb1Mrl2M3jSlLKLRI9GxjPIju1KqgW4a4oKqPVrLzupbMZq+RZ1Ct9V+lSYVMOUHNUb8PaurjIwcGjMQYmsy3yTXQS+pdyPOX+UllnRAD7QTCEj9gGdo/U= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033037009110;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0X0Fooxo_1775100746; Received: from 30.221.145.69(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0X0Fooxo_1775100746 cluster:ay36) by smtp.aliyun-inc.com; Thu, 02 Apr 2026 11:32:27 +0800 Message-ID: Date: Thu, 2 Apr 2026 11:32:25 +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 v3] 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: 8bit On 4/2/26 11:10 AM, 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        |  6 +++--- >  fs/ocfs2/ocfs2_trace.h | 10 ++++------ >  2 files changed, 7 insertions(+), 9 deletions(-) > > diff --git a/fs/ocfs2/mmap.c b/fs/ocfs2/mmap.c > index 50e2faf64c..41c08c5a3d 100644 > --- a/fs/ocfs2/mmap.c > +++ b/fs/ocfs2/mmap.c > @@ -30,7 +30,7 @@ >   >  static vm_fault_t ocfs2_fault(struct vm_fault *vmf) >  { > - struct vm_area_struct *vma = vmf->vma; > + struct inode *inode = file_inode(vmf->vma->vm_file); >   sigset_t oldset; >   vm_fault_t ret; >   > @@ -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, > +     vmf->page, vmf->pgoff); Seems malformed? >   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) Ditto. >  ); >   >  /* End of trace events for fs/ocfs2/mmap.c. */ > -- > 2.53.0 >