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Message-ID: <20191011144834.GL16384@42.do-not-panic.com>
Date: Fri, 11 Oct 2019 14:48:34 +0000
From: Luis Chamberlain <mcgrof@...nel.org>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Darren Hart <dvhart@...radead.org>,
Andy Shevchenko <andy@...radead.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Rafael J . Wysocki" <rafael@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H . Peter Anvin" <hpa@...or.com>,
Jonathan Corbet <corbet@....net>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
Peter Jones <pjones@...hat.com>,
Dave Olsthoorn <dave@...aar.me>, x86@...nel.org,
platform-driver-x86@...r.kernel.org, linux-efi@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
linux-input@...r.kernel.org
Subject: Re: [PATCH v7 2/8] efi: Add embedded peripheral firmware support
On Fri, Oct 04, 2019 at 04:50:50PM +0200, Hans de Goede wrote:
> +static int __init efi_check_md_for_embedded_firmware(
> + efi_memory_desc_t *md, const struct efi_embedded_fw_desc *desc)
> +{
> + const u64 prefix = *((u64 *)desc->prefix);
> + struct sha256_state sctx;
> + struct embedded_fw *fw;
> + u8 sha256[32];
> + u64 i, size;
> + void *map;
> +
> + size = md->num_pages << EFI_PAGE_SHIFT;
> + map = memremap(md->phys_addr, size, MEMREMAP_WB);
Since our limitaiton is the init process must have mostly finished,
it implies early x86 boot code cannot use this, what measures can we
take to prevent / check for such conditions to be detected and
gracefully errored out?
> + if (!map) {
> + pr_err("Error mapping EFI mem at %#llx\n", md->phys_addr);
> + return -ENOMEM;
> + }
> +
> + size -= desc->length;
Remind me again, why we decrement the size here?
I was going to ask if we didn't need a:
if (desc->length > size) {
memunmap(map);
return -EINVAL;
}
> + for (i = 0; i < size; i += 8) {
> + u64 *mem = map + i;
> +
> + if (*mem != prefix)
> + continue;
> +
> + sha256_init(&sctx);
> + sha256_update(&sctx, map + i, desc->length);
> + sha256_final(&sctx, sha256);
> + if (memcmp(sha256, desc->sha256, 32) == 0)
> + break;
> + }
> + if (i >= size) {
> + memunmap(map);
> + return -ENOENT;
> + }
> +
> + pr_info("Found EFI embedded fw '%s'\n", desc->name);
Otherwise looks good.
Luis
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