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From: Matthew Wilcox <willy@infradead.org>
To: Topi Miettinen <toiwoton@gmail.com>
Cc: linux-hardening@vger.kernel.org, akpm@linux-foundation.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Andy Lutomirski <luto@kernel.org>, Jann Horn <jannh@google.com>,
	Kees Cook <keescook@chromium.org>,
	Linux API <linux-api@vger.kernel.org>,
	Mike Rapoport <rppt@kernel.org>
Subject: Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations
Date: Wed, 2 Dec 2020 18:53:34 +0000	[thread overview]
Message-ID: <20201202185334.GG11935@casper.infradead.org> (raw)
In-Reply-To: <20201201214547.9721-1-toiwoton@gmail.com>

On Tue, Dec 01, 2020 at 11:45:47PM +0200, Topi Miettinen wrote:
> +	/* Randomize allocation */
> +	if (randomize_vmalloc) {
> +		voffset = get_random_long() & (roundup_pow_of_two(vend - vstart) - 1);
> +		voffset = PAGE_ALIGN(voffset);
> +		if (voffset + size > vend - vstart)
> +			voffset = vend - vstart - size;
> +	} else
> +		voffset = 0;
> +
>  	/*
>  	 * If an allocation fails, the "vend" address is
>  	 * returned. Therefore trigger the overflow path.
>  	 */
> -	addr = __alloc_vmap_area(size, align, vstart, vend);
> +	addr = __alloc_vmap_area(size, align, vstart + voffset, vend);
>  	spin_unlock(&free_vmap_area_lock);

What if there isn't any free address space between vstart+voffset and
vend, but there is free address space between vstart and voffset?
Seems like we should add:

	addr = __alloc_vmap_area(size, align, vstart + voffset, vend);
+	if (!addr)
+		addr = __alloc_vmap_area(size, align, vstart, vend);
	spin_unlock(&free_vmap_area_lock);

  parent reply	other threads:[~2020-12-02 18:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-01 21:45 Topi Miettinen
2020-12-02 18:49 ` Topi Miettinen
2020-12-03  6:58   ` Mike Rapoport
2020-12-03 23:15     ` David Laight
2020-12-04 10:58       ` Topi Miettinen
2020-12-04 13:33         ` David Laight
2020-12-04 16:53           ` Topi Miettinen
2020-12-09 19:08     ` Topi Miettinen
2020-12-10 19:58     ` Topi Miettinen
2020-12-02 18:53 ` Matthew Wilcox [this message]
2020-12-02 21:28   ` Topi Miettinen

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