Re: [PATCH] mm, kasan: don't poison boot memory

From: Mike Rapoport <rppt@linux.ibm.com>
To: George Kennedy <george.kennedy@oracle.com>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Marco Elver <elver@google.com>,
	Dhaval Giani <dhaval.giani@oracle.com>,
	David Hildenbrand <david@redhat.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Branislav Rankov <Branislav.Rankov@arm.com>,
	kasan-dev <kasan-dev@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Alexander Potapenko <glider@google.com>,
	Evgenii Stepanov <eugenis@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Konrad Rzeszutek Wilk <konrad@darnok.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Peter Collingbourne <pcc@google.com>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH] mm, kasan: don't poison boot memory
Date: Tue, 23 Feb 2021 22:09:14 +0200	[thread overview]
Message-ID: <20210223200914.GH1741768@linux.ibm.com> (raw)
In-Reply-To: <3a56ba38-ce91-63a6-b57c-f1726aa1b76e@oracle.com>

On Tue, Feb 23, 2021 at 01:05:05PM -0500, George Kennedy wrote:
> On 2/23/2021 10:47 AM, Mike Rapoport wrote:
> 
> It now crashes here:
> 
> [    0.051019] ACPI: Early table checksum verification disabled
> [    0.056721] ACPI: RSDP 0x00000000BFBFA014 000024 (v02 BOCHS )
> [    0.057874] ACPI: XSDT 0x00000000BFBF90E8 00004C (v01 BOCHS BXPCFACP
> 00000001      01000013)
> [    0.059590] ACPI: FACP 0x00000000BFBF5000 000074 (v01 BOCHS BXPCFACP
> 00000001 BXPC 00000001)
> [    0.061306] ACPI: DSDT 0x00000000BFBF6000 00238D (v01 BOCHS BXPCDSDT
> 00000001 BXPC 00000001)
> [    0.063006] ACPI: FACS 0x00000000BFBFD000 000040
> [    0.063938] ACPI: APIC 0x00000000BFBF4000 000090 (v01 BOCHS BXPCAPIC
> 00000001 BXPC 00000001)
> [    0.065638] ACPI: HPET 0x00000000BFBF3000 000038 (v01 BOCHS BXPCHPET
> 00000001 BXPC 00000001)
> [    0.067335] ACPI: BGRT 0x00000000BE49B000 000038 (v01 INTEL EDK2    
> 00000002      01000013)
> [    0.069030] ACPI: iBFT 0x00000000BE453000 000800 (v01 BOCHS BXPCFACP
> 00000000      00000000)
> [    0.070734] XXX acpi_find_ibft_region:
> [    0.071468] XXX iBFT, status=0
> [    0.072073] XXX about to call acpi_put_table()...
> ibft_addr=ffffffffff240000
> [    0.073449] XXX acpi_find_ibft_region(EXIT):
> PANIC: early exception 0x0e IP 10:ffffffff9259f439 error 0 cr2
> 0xffffffffff240004

Right, I've missed the dereference of the ibft_addr after
acpi_find_ibft_region(). 

With this change to iscsi_ibft_find.c instead of the previous one it should
be better:

diff --git a/drivers/firmware/iscsi_ibft_find.c b/drivers/firmware/iscsi_ibft_find.c
index 64bb94523281..1be7481d5c69 100644
--- a/drivers/firmware/iscsi_ibft_find.c
+++ b/drivers/firmware/iscsi_ibft_find.c
@@ -80,6 +80,27 @@ static int __init find_ibft_in_mem(void)
 done:
 	return len;
 }
+
+static void __init acpi_find_ibft_region(unsigned long *sizep)
+{
+	int i;
+	struct acpi_table_header *table = NULL;
+	acpi_status status;
+
+	if (acpi_disabled)
+		return;
+
+	for (i = 0; i < ARRAY_SIZE(ibft_signs) && !ibft_addr; i++) {
+		status = acpi_get_table(ibft_signs[i].sign, 0, &table);
+		if (ACPI_SUCCESS(status)) {
+			ibft_addr = (struct acpi_table_ibft *)table;
+			*sizep = PAGE_ALIGN(ibft_addr->header.length);
+			acpi_put_table(table);
+			break;
+		}
+	}
+}
+
 /*
  * Routine used to find the iSCSI Boot Format Table. The logical
  * kernel address is set in the ibft_addr global variable.
@@ -91,14 +112,16 @@ unsigned long __init find_ibft_region(unsigned long *sizep)
 	/* iBFT 1.03 section 1.4.3.1 mandates that UEFI machines will
 	 * only use ACPI for this */
 
-	if (!efi_enabled(EFI_BOOT))
+	if (!efi_enabled(EFI_BOOT)) {
 		find_ibft_in_mem();
-
-	if (ibft_addr) {
 		*sizep = PAGE_ALIGN(ibft_addr->header.length);
-		return (u64)virt_to_phys(ibft_addr);
+	} else {
+		acpi_find_ibft_region(sizep);
 	}
 
+	if (ibft_addr)
+		return (u64)virt_to_phys(ibft_addr);
+
 	*sizep = 0;
 	return 0;
 }

> [    0.075711] CPU: 0 PID: 0 Comm: swapper Not tainted 5.11.0-34a2105 #8
> [    0.076983] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
> 0.0.0 02/06/2015
> [    0.078579] RIP: 0010:find_ibft_region+0x470/0x577

-- 
Sincerely yours,
Mike.

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