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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Steven Clarkson <sc@lambdal.com>,
        Borislav Petkov <bp@suse.de>, linux-acpi@vger.kernel.org,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.4 34/96] x86/boot: Handle malformed SRAT tables during early ACPI parsing
Date:   Thu, 13 Feb 2020 07:20:41 -0800
Message-Id: <20200213151852.168079621@linuxfoundation.org>
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From: Steven Clarkson <sc@lambdal.com>

[ Upstream commit 2b73ea3796242608b4ccf019ff217156c92e92fe ]

Break an infinite loop when early parsing of the SRAT table is caused
by a subtable with zero length. Known to affect the ASUS WS X299 SAGE
motherboard with firmware version 1201 which has a large block of
zeros in its SRAT table. The kernel could boot successfully on this
board/firmware prior to the introduction of early parsing this table or
after a BIOS update.

 [ bp: Fixup whitespace damage and commit message. Make it return 0 to
   denote that there are no immovable regions because who knows what
   else is broken in this BIOS. ]

Fixes: 02a3e3cdb7f1 ("x86/boot: Parse SRAT table and count immovable memory regions")
Signed-off-by: Steven Clarkson <sc@lambdal.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: linux-acpi@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206343
Link: https://lkml.kernel.org/r/CAHKq8taGzj0u1E_i=poHUam60Bko5BpiJ9jn0fAupFUYexvdUQ@mail.gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/boot/compressed/acpi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 25019d42ae937..ef2ad7253cd5e 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -393,7 +393,13 @@ int count_immovable_mem_regions(void)
 	table = table_addr + sizeof(struct acpi_table_srat);
 
 	while (table + sizeof(struct acpi_subtable_header) < table_end) {
+
 		sub_table = (struct acpi_subtable_header *)table;
+		if (!sub_table->length) {
+			debug_putstr("Invalid zero length SRAT subtable.\n");
+			return 0;
+		}
+
 		if (sub_table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {
 			struct acpi_srat_mem_affinity *ma;
 
-- 
2.20.1