linux-kernel - Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

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Message-ID: <20191225113932.GD18098@zn.tnic>
Date:   Wed, 25 Dec 2019 12:39:32 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     linux-kernel@...r.kernel.org
Cc:     linux-tip-commits@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, x86 <x86@...nel.org>
Subject: Re: [tip: core/urgent] rseq: Reject unknown flags on rseq unregister

On Wed, Dec 25, 2019 at 10:38:53AM -0000, tip-bot2 for Mathieu Desnoyers wrote:
> The following commit has been merged into the core/urgent branch of tip:
> 
> Commit-ID:     66528a4575eee9f5a5270219894ab6178f146e84
> Gitweb:        https://git.kernel.org/tip/66528a4575eee9f5a5270219894ab6178f146e84
> Author:        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> AuthorDate:    Wed, 11 Dec 2019 11:17:11 -05:00
> Committer:     Ingo Molnar <mingo@...nel.org>
> CommitterDate: Wed, 25 Dec 2019 10:41:20 +01:00
> 
> rseq: Reject unknown flags on rseq unregister
> 
> It is preferrable to reject unknown flags within rseq unregistration
> rather than to ignore them. It is an oversight caused by the fact that
> the check for unknown flags is after the rseq unregister flag check.
> 
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Link: https://lkml.kernel.org/r/20191211161713.4490-2-mathieu.desnoyers@efficios.com
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  kernel/rseq.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/kernel/rseq.c b/kernel/rseq.c
> index 27c48eb..a4f86a9 100644
> --- a/kernel/rseq.c
> +++ b/kernel/rseq.c
> @@ -310,6 +310,8 @@ SYSCALL_DEFINE4(rseq, struct rseq __user *, rseq, u32, rseq_len,
>  	int ret;
>  
>  	if (flags & RSEQ_FLAG_UNREGISTER) {
> +		if (flags & ~RSEQ_FLAG_UNREGISTER)
> +			return -EINVAL;
>  		/* Unregister rseq for current thread. */
>  		if (current->rseq != rseq || !current->rseq)
>  			return -EINVAL;

Cc: stable perhaps?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette