linux-kernel - Re: drivers/block/rbd.c: atomic_inc_return_safe() & atomic_dec_return

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]

Message-ID: <c2dd3223-bda1-be8c-fbc4-9c0eec63bc9d@kernel.dk>
Date:   Fri, 2 Oct 2020 17:44:22 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Shuah Khan <skhan@...uxfoundation.org>, idryomov@...il.com,
        dongsheng.yang@...ystack.cn
Cc:     ceph-devel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: drivers/block/rbd.c: atomic_inc_return_safe() &
 atomic_dec_return_safe()

On 10/2/20 4:34 PM, Shuah Khan wrote:
> All,
> 
> I came across these atomic_inc_return_safe() & atomic_dec_return_safe()
> functions that hold the counters at safe values.
> 
> atomic_inc_return_safe()
> 
> If the counter is already 0 it will not be incremented.
> If the counter is already at its maximum value returns
> -EINVAL without updating it.
> 
> atomic_dec_return_safe()
> 
> Decrement the counter.  Return the resulting value, or -EINVAL
> 
> These two routines are static and only used in rbd.c.
> 
> Can these become part of atomic_t ops?

I think you just want to use refcount_t for this use case. They
have safe guards for under/overflow.

-- 
Jens Axboe