linux-kernel - Re: [RFCv2 1/9] efi/libstub: Ask efi_random

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Message-Id: <D3K31JJ5PZQG.2XW6Y6OR1CTLG@kernel.org>
Date: Mon, 19 Aug 2024 21:00:08 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Pingfan Liu" <piliu@...hat.com>, <linux-efi@...r.kernel.org>
Cc: "Ard Biesheuvel" <ardb@...nel.org>, "Jan Hendrik Farr"
 <kernel@...rr.cc>, "Philipp Rudo" <prudo@...hat.com>, "Lennart Poettering"
 <mzxreary@...inter.de>, "Eric Biederman" <ebiederm@...ssion.com>, "Baoquan
 He" <bhe@...hat.com>, "Dave Young" <dyoung@...hat.com>, "Mark Rutland"
 <mark.rutland@....com>, "Will Deacon" <will@...nel.org>, "Catalin Marinas"
 <catalin.marinas@....com>, <kexec@...ts.infradead.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [RFCv2 1/9] efi/libstub: Ask efi_random_alloc() to skip
 unusable memory

On Mon Aug 19, 2024 at 5:53 PM EEST, Pingfan Liu wrote:
> efi_random_alloc() demands EFI_ALLOCATE_ADDRESS when allocate_pages(),
> but the current implement can not ensure the selected target locates
> inside free area, that is to exclude EFI_BOOT_SERVICES_*,
> EFI_RUNTIME_SERVICES_* etc.
>
> Fix the issue by checking md->type.

If it is a fix shouldn't this have a fixes tag?

>
> Signed-off-by: Pingfan Liu <piliu@...hat.com>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> To: linux-efi@...r.kernel.org
> ---
>  drivers/firmware/efi/libstub/randomalloc.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> index c41e7b2091cdd..7304e767688f2 100644
> --- a/drivers/firmware/efi/libstub/randomalloc.c
> +++ b/drivers/firmware/efi/libstub/randomalloc.c
> @@ -79,6 +79,8 @@ efi_status_t efi_random_alloc(unsigned long size,
>  		efi_memory_desc_t *md = (void *)map->map + map_offset;
>  		unsigned long slots;
>  

I'd add this inline comment:

/* Skip "unconventional" memory: */

> +		if (!(md->type & (EFI_CONVENTIONAL_MEMORY || EFI_PERSISTENT_MEMORY)))
> +			continue;
>  		slots = get_entry_num_slots(md, size, ilog2(align), alloc_min,
>  					    alloc_max);
>  		MD_NUM_SLOTS(md) = slots;
> @@ -111,6 +113,9 @@ efi_status_t efi_random_alloc(unsigned long size,
>  		efi_physical_addr_t target;
>  		unsigned long pages;
>  
> +		if (!(md->type & (EFI_CONVENTIONAL_MEMORY || EFI_PERSISTENT_MEMORY)))
> +			continue;
> +
>  		if (total_mirrored_slots > 0 &&
>  		    !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
>  			continue;

BR, Jarkko