From: Baoquan He <bhe@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, hpa@zytor.com,
mingo@kernel.org, keescook@chromium.org, thgarnie@google.com,
caoj.fnst@cn.fujitsu.com, izumi.taku@jp.fujitsu.com
Subject: Re: [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
Date: Tue, 4 Jul 2017 22:30:34 +0800 [thread overview]
Message-ID: <20170704143034.GA25192@x1> (raw)
In-Reply-To: <alpine.DEB.2.20.1707041555570.9000@nanos>
On 07/04/17 at 04:00pm, Thomas Gleixner wrote:
> On Tue, 4 Jul 2017, Baoquan He wrote:
> > +/* Marks if efi mirror regions have been found and handled. */
> > +static bool efi_mirror_found;
> > +
> > +static void process_efi_entry(unsigned long minimum, unsigned long image_size)
> > +{
> > + struct efi_info *e = &boot_params->efi_info;
> > + struct mem_vector region;
> > + efi_memory_desc_t *md;
> > + unsigned long pmap;
> > + char *signature;
> > + u32 nr_desc;
> > + int i;
> > +
> > +
> > +#ifdef CONFIG_EFI
> > + signature = (char *)&boot_params->efi_info.efi_loader_signature;
> > +#endif
>
> So if CONFIG_EFI=n you happily dereference the uninitialized signature
> pointer ...
Right, this is a mistake. Thanks for pointing it out. I should have
checked if the pointer is NULL.
In fact I just referred to code in setup_arch(). Now I have a question,
though CONFIG_EFI=y but efi firmware is not enabled,
boot_params.efi_info.efi_loader_signature should be initilized to 0.
Then below code is also problematic.
#ifdef CONFIG_EFI
if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
EFI32_LOADER_SIGNATURE, 4)) {
set_bit(EFI_BOOT, &efi.flags);
} else if (!strncmp((char *)&boot_params.efi_info.efi_loader_signature,
EFI64_LOADER_SIGNATURE, 4)) {
set_bit(EFI_BOOT, &efi.flags);
set_bit(EFI_64BIT, &efi.flags);
}
if (efi_enabled(EFI_BOOT))
efi_memblock_x86_reserve_range();
#endif
>
> Why is process_efi_entry() invoked at all if EFI is not enabled?
Yeah, and it's better to check if CONFIG_EFI is enabled before
invocation of process_efi_entry(). Let me change it as below and repost.
Thanks again for looking into this patchset.
+#ifdef CONFIG_EFI
process_efi_entry(minimum, image_size);
+#endif
>
> > + if (strncmp(signature, EFI32_LOADER_SIGNATURE, 4) &&
> > + strncmp(signature, EFI64_LOADER_SIGNATURE, 4))
> > + return;
> > +
>
> Thanks,
>
> tglx
next prev parent reply other threads:[~2017-07-04 14:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-04 8:04 [PATCH v2 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He
2017-07-04 8:04 ` [PATCH v2 1/2] x86/boot/KASLR: Adapt process_e820_entry for any type of memory entry Baoquan He
2017-07-05 22:06 ` Kees Cook
2017-07-06 1:21 ` Baoquan He
2017-07-04 8:04 ` [PATCH v2 2/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He
2017-07-04 14:00 ` Thomas Gleixner
2017-07-04 14:30 ` Baoquan He [this message]
2017-07-04 14:46 ` Thomas Gleixner
2017-07-04 15:36 ` Matt Fleming
2017-07-04 15:46 ` Thomas Gleixner
2017-07-04 23:16 ` Baoquan He
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