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

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Date:   Wed, 6 May 2020 10:59:55 +0530
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     Guo Ren <guoren@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.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

* 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 and Regards
Srikar Dronamraju