linux-kernel - Re: nfs mmap adventure (was: 2.6.23-mm1)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 15 Oct 2007 11:51:29 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	David Howells <dhowells@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: nfs mmap adventure (was: 2.6.23-mm1)


On Mon, 2007-10-15 at 15:06 +0100, David Howells wrote:
> Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > I get funny SIGBUS' like so:
> > 
> > fault
> >   if (->page_mkwrite() < 0)
> >     nfs_vm_page_mkwrite()
> >       nfs_write_begin()
> >         nfs_flush_incompatible()
> >           nfs_wb_page()
> >             nfs_wb_page_priority()
> >               nfs_sync_mapping_wait()
> >                 nfs_wait_on_request_locked()
> >                   nfs_wait_on_request()
> >                     nfs_wait_bit_interruptible()
> >                       return -ERESTARTSYS
> >     SIGBUS
> > 
> > trying to figure out what to do about this...
> > 
> 
> Hmmm...  It sounds like the fault handler should deliver the appropriate
> signal, should ->page_mkwrite() return ERESTARTSYS, and then retry the access
> instruction that caused the fault when the signal handler has finished
> running.

If you signal the process before msync() has completed, or before you
have completed unmapping the region then your writes can potentially be
lost. Why should we be providing any guarantees beyond that?

Trond

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/