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From: Eugene Korenevsky <ekorenevsky@gmail.com>
To: kzak@redhat.com
Cc: David.Laight@aculab.com, Davidlohr Bueso <dave@stgolabs.net>,
	linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: Re: [PATCH v2] efi: take size of partition entry from GPT header
Date: Sat, 6 Oct 2018 21:41:27 +0300	[thread overview]
Message-ID: <CAJC2YLYqb6WB43P5pJe=D7GXgUY16PS=QLVJbD8=qEH=aB9qvg@mail.gmail.com> (raw)
In-Reply-To: <20180914110703.ishvqwcpcf5ozihy@ws.net.home>

> is_gpt_valid() already contains
>         pt_size = (u64)le32_to_cpu((*gpt)->num_partition_entries) *
>                 le32_to_cpu((*gpt)->sizeof_partition_entry);
>         if (pt_size > KMALLOC_MAX_SIZE)
>                 pr_debug("GUID Partition Table is too large: %llu > %lu bytes\n",
>                 (unsigned long long)pt_size, KMALLOC_MAX_SIZE);
>                 goto fail;
>         }
> I guess it good enough for sanity check.
>
> If you want to be really paranoid than you can also check that array
> is possible to store to the expected area on the disk:
>
>     pt_size <= (gpt->first_usable_lba - gpt->partition_entry_lba)
>

Well, we should apply several checks for different cases:
- primary GPT: table entries should not override gpt->first_usable_lba
- alternate GPT, table entries BEFORE agpt (agpt->partition_entry_lba
< agpt_lba): table entries should not override agpt_lba AND
agpt->partition_entry_lba MUST BE more than agpt->last_usable_lba
- alternate GPT, table entries AFTER agpt (agpt->partition_entry_lba >
agpt_lba): table entries should not override the end of the disk

Is this correct?

--
Eugene

  reply	other threads:[~2018-10-06 18:41 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-11 16:15 [PATCH v2] efi: take size of partition entry from GPT header Eugene Korenevsky
2018-09-11 16:27 ` Davidlohr Bueso
2018-09-11 16:42   ` Eugene Korenevsky
2018-09-11 22:56 ` kbuild test robot
2018-09-11 22:59 ` Ard Biesheuvel
2018-09-11 23:20 ` kbuild test robot
2018-09-12  8:38 ` Karel Zak
2018-09-13 13:06   ` David Laight
2018-09-13 19:48     ` Eugene Korenevsky
2018-09-14  9:01       ` David Laight
2018-09-14 11:07         ` kzak
2018-10-06 18:41           ` Eugene Korenevsky [this message]
2018-10-08 11:15             ` Karel Zak

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