From: Nicolai Stange <nicstange@gmail.com> To: Dave Young <dyoung@redhat.com> Cc: Nicolai Stange <nicstange@gmail.com>, Matt Fleming <matt@codeblueprint.co.uk>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org, Ingo Molnar <mingo@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, hpa@zytor.com, Dan Williams <dan.j.williams@intel.com>, mika.penttila@nextfour.com, bhsharma@redhat.com Subject: Re: [PATCH 2/4] efi/x86: move efi bgrt init code to early init code Date: Fri, 13 Jan 2017 00:11:53 +0100 [thread overview] Message-ID: <87shonooue.fsf@gmail.com> (raw) In-Reply-To: <20170112213939.GD2709@dhcp-128-65.nay.redhat.com> (Dave Young's message of "Fri, 13 Jan 2017 05:39:39 +0800") On Fri, Jan 13 2017, Dave Young wrote: > On 01/12/17 at 12:54pm, Nicolai Stange wrote: >> On Thu, Jan 12 2017, Dave Young wrote: >> >> > -void __init efi_bgrt_init(void) >> > +void __init efi_bgrt_init(struct acpi_table_header *table) >> > { >> > - acpi_status status; >> > void *image; >> > struct bmp_header bmp_header; >> > >> > if (acpi_disabled) >> > return; >> > >> > - status = acpi_get_table("BGRT", 0, >> > - (struct acpi_table_header **)&bgrt_tab); >> > - if (ACPI_FAILURE(status)) >> > - return; >> >> >> Not sure, but wouldn't it be safer to reverse the order of this assignment >> >> > + bgrt_tab = *(struct acpi_table_bgrt *)table; > > Nicolai, sorry, I'm not sure I understand the comment, is it about above line? > Could you elaborate a bit? > >> >> and this length check >> > > I also do not get this :( Ah sorry, my point is this: the length check should perhaps be made before doing the assignment to bgrt_tab because otherwise, we might end up reading from invalid memory. I.e. if (struct acpi_table_bgrt *)table->length < sizeof(bgrt_tab), then bgrt_tab = *(struct acpi_table_bgrt *)table; would read past the table's end. I'm not sure whether this is a real problem though -- that is, whether this read could ever hit some unmapped memory. >> > - if (bgrt_tab->header.length < sizeof(*bgrt_tab)) { >> > + if (bgrt_tab.header.length < sizeof(bgrt_tab)) { >> > pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n", >> > - bgrt_tab->header.length, sizeof(*bgrt_tab)); >> > + bgrt_tab.header.length, sizeof(bgrt_tab)); >> > return; >> > } >> >> ? Thanks, Nicolai
WARNING: multiple messages have this Message-ID (diff)
From: Nicolai Stange <nicstange-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> To: Dave Young <dyoung-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> Cc: Nicolai Stange <nicstange-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Matt Fleming <matt-mF/unelCI9GS6iBeEJttW/XRex20P6io@public.gmane.org>, Ard Biesheuvel <ard.biesheuvel-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>, linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, mika.penttila-MRsr7dthA9VWk0Htik3J/w@public.gmane.org, bhsharma-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org Subject: Re: [PATCH 2/4] efi/x86: move efi bgrt init code to early init code Date: Fri, 13 Jan 2017 00:11:53 +0100 [thread overview] Message-ID: <87shonooue.fsf@gmail.com> (raw) In-Reply-To: <20170112213939.GD2709-0VdLhd/A9Pl+NNSt+8eSiB/sF2h8X+2i0E9HWUfgJXw@public.gmane.org> (Dave Young's message of "Fri, 13 Jan 2017 05:39:39 +0800") On Fri, Jan 13 2017, Dave Young wrote: > On 01/12/17 at 12:54pm, Nicolai Stange wrote: >> On Thu, Jan 12 2017, Dave Young wrote: >> >> > -void __init efi_bgrt_init(void) >> > +void __init efi_bgrt_init(struct acpi_table_header *table) >> > { >> > - acpi_status status; >> > void *image; >> > struct bmp_header bmp_header; >> > >> > if (acpi_disabled) >> > return; >> > >> > - status = acpi_get_table("BGRT", 0, >> > - (struct acpi_table_header **)&bgrt_tab); >> > - if (ACPI_FAILURE(status)) >> > - return; >> >> >> Not sure, but wouldn't it be safer to reverse the order of this assignment >> >> > + bgrt_tab = *(struct acpi_table_bgrt *)table; > > Nicolai, sorry, I'm not sure I understand the comment, is it about above line? > Could you elaborate a bit? > >> >> and this length check >> > > I also do not get this :( Ah sorry, my point is this: the length check should perhaps be made before doing the assignment to bgrt_tab because otherwise, we might end up reading from invalid memory. I.e. if (struct acpi_table_bgrt *)table->length < sizeof(bgrt_tab), then bgrt_tab = *(struct acpi_table_bgrt *)table; would read past the table's end. I'm not sure whether this is a real problem though -- that is, whether this read could ever hit some unmapped memory. >> > - if (bgrt_tab->header.length < sizeof(*bgrt_tab)) { >> > + if (bgrt_tab.header.length < sizeof(bgrt_tab)) { >> > pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n", >> > - bgrt_tab->header.length, sizeof(*bgrt_tab)); >> > + bgrt_tab.header.length, sizeof(bgrt_tab)); >> > return; >> > } >> >> ? Thanks, Nicolai
next prev parent reply other threads:[~2017-01-12 23:12 UTC|newest] Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-01-12 9:41 [PATCH 0/4] efi/x86: move efi bgrt init code to early init Dave Young 2017-01-12 9:41 ` [PATCH 1/4] efi/x86: make efi_memmap_reserve only insert into boot mem areas Dave Young 2017-01-12 9:41 ` Dave Young 2017-01-12 11:15 ` Nicolai Stange 2017-01-12 11:15 ` Nicolai Stange 2017-01-12 21:29 ` Dave Young 2017-01-12 21:29 ` Dave Young 2017-01-27 14:48 ` Matt Fleming 2017-01-27 17:04 ` Ard Biesheuvel 2017-01-27 17:04 ` Ard Biesheuvel 2017-01-27 22:13 ` Matt Fleming 2017-01-27 22:13 ` Matt Fleming 2017-01-27 22:15 ` Ard Biesheuvel 2017-01-27 22:15 ` Ard Biesheuvel 2017-01-12 16:15 ` Ard Biesheuvel 2017-01-12 16:15 ` Ard Biesheuvel 2017-01-12 21:20 ` Dave Young 2017-01-12 21:20 ` Dave Young 2017-01-13 8:10 ` Dave Young 2017-01-12 9:41 ` [PATCH 2/4] efi/x86: move efi bgrt init code to early init code Dave Young 2017-01-12 9:56 ` Dave Young 2017-01-12 11:54 ` Nicolai Stange 2017-01-12 11:54 ` Nicolai Stange 2017-01-12 21:39 ` Dave Young 2017-01-12 23:11 ` Nicolai Stange [this message] 2017-01-12 23:11 ` Nicolai Stange 2017-01-13 2:21 ` Dave Young 2017-01-13 3:04 ` Dave Young 2017-01-13 3:04 ` Dave Young 2017-01-13 12:21 ` Nicolai Stange 2017-01-13 12:21 ` Nicolai Stange 2017-01-16 2:55 ` Dave Young 2017-01-16 2:55 ` Dave Young 2017-01-12 16:20 ` Ard Biesheuvel 2017-01-12 16:20 ` Ard Biesheuvel 2017-01-12 21:33 ` Dave Young 2017-01-12 21:33 ` Dave Young 2017-01-16 15:15 ` Bhupesh Sharma 2017-01-17 17:00 ` Ard Biesheuvel 2017-01-12 9:41 ` [PATCH 3/4] efi/x86: move efi_print_memmap to drivers/firmware/efi/memmap.c Dave Young 2017-01-12 9:41 ` Dave Young 2017-01-12 12:08 ` Nicolai Stange 2017-01-12 21:40 ` Dave Young 2017-01-12 9:41 ` [PATCH 4/4] efi/x86: add debug code to print cooked memmap Dave Young 2017-01-12 16:18 ` Ard Biesheuvel
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