linux-kernel - Re: [PATCH] uprobes: ensure that uprobe->offset and ->ref_ctr

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Message-ID: <20200506085141.723673f1@gandalf.local.home>
Date:   Wed, 6 May 2020 08:51:41 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     Oleg Nesterov <oleg@...hat.com>, Guo Ren <guoren@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Jann Horn <jannh@...gle.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>,
        Security Officers <security@...nel.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Ananth N Mavinakayanahalli <ananth@...ibm.com>,
        Naveen Rao <naveen.n.rao@...ux.vnet.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes: ensure that uprobe->offset and
 ->ref_ctr_offset are properly aligned

On Wed, 6 May 2020 10:59:55 +0530
Srikar Dronamraju <srikar@...ux.vnet.ibm.com> wrote:

> * Oleg Nesterov <oleg@...hat.com> [2020-05-04 18:47:25]:
> 
> > uprobe_write_opcode() must not cross page boundary; prepare_uprobe()
> > relies on arch_uprobe_analyze_insn() which should validate "vaddr" but
> > some architectures (csky, s390, and sparc) don't do this.
> > 
> > We can remove the BUG_ON() check in prepare_uprobe() and validate the
> > offset early in __uprobe_register(). The new IS_ALIGNED() check matches
> > the alignment check in arch_prepare_kprobe() on supported architectures,
> > so I think that all insns must be aligned to UPROBE_SWBP_INSN_SIZE.
> > 
> > Another problem is __update_ref_ctr() which was wrong from the very
> > beginning, it can read/write outside of kmap'ed page unless "vaddr" is
> > aligned to sizeof(short), __uprobe_register() should check this too.
> > 
> > Cc: stable@...r.kernel.org
> > Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>  
> 
> Thanks Oleg.
> 
> Looks good to me.
> 
> Reviewed-by: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
> > ---  
> 

Thanks Oleg, Srikar and Sven.

As this is in the kernel/events/ directory, I'm guessing it should be taken
through the tip tree?

-- Steve