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    Subject[PATCH 5.4 34/96] x86/boot: Handle malformed SRAT tables during early ACPI parsing
    Date
    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


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