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| author | Vit Kabele <vit@kabele.me> | 2022-10-27 19:50:59 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2022-10-28 17:28:22 +0200 |
| commit | 8ff2906513f5ad2f6665b94d1763a26e30bfa47b (patch) | |
| tree | 6f9a96da2a40a1148337bef3bdbf3eb119f59591 /drivers/acpi/acpica | |
| parent | ACPICA: Check that EBDA pointer is in valid memory (diff) | |
| download | linux-8ff2906513f5ad2f6665b94d1763a26e30bfa47b.tar.xz linux-8ff2906513f5ad2f6665b94d1763a26e30bfa47b.zip | |
ACPICA: Do not touch VGA memory when EBDA < 1ki_b
ACPICA commit a36eda9631e84f271319c41288889dd5b1329369
The ACPICA code assumes that EBDA region must be at least 1ki_b in size.
Because this is not guaranteed, it might happen that while scanning the
memory for RSDP pointer, the kernel touches memory above 640ki_b.
This is unwanted as the VGA memory range may not be decoded or
even present when running under virtualization.
Link: https://github.com/acpica/acpica/commit/a36eda96
Signed-off-by: Vit Kabele <vit@kabele.me>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/acpica')
| -rw-r--r-- | drivers/acpi/acpica/tbxfroot.c | 22 |
1 files changed, 15 insertions, 7 deletions
diff --git a/drivers/acpi/acpica/tbxfroot.c b/drivers/acpi/acpica/tbxfroot.c index ede2745838c8..f1c2ab0a4561 100644 --- a/drivers/acpi/acpica/tbxfroot.c +++ b/drivers/acpi/acpica/tbxfroot.c @@ -114,6 +114,7 @@ acpi_find_root_pointer(acpi_physical_address *table_address) u8 *table_ptr; u8 *mem_rover; u32 physical_address; + u32 ebda_window_size; ACPI_FUNCTION_TRACE(acpi_find_root_pointer); @@ -145,24 +146,31 @@ acpi_find_root_pointer(acpi_physical_address *table_address) */ if (physical_address > 0x400 && physical_address < 0xA0000) { /* - * 1b) Search EBDA paragraphs (EBDA is required to be a - * minimum of 1K length) + * Calculate the scan window size + * The EBDA is not guaranteed to be larger than a ki_b and in case + * that it is smaller, the scanning function would leave the low + * memory and continue to the VGA range. + */ + ebda_window_size = ACPI_MIN(ACPI_EBDA_WINDOW_SIZE, + 0xA0000 - physical_address); + + /* + * 1b) Search EBDA paragraphs */ table_ptr = acpi_os_map_memory((acpi_physical_address) physical_address, - ACPI_EBDA_WINDOW_SIZE); + ebda_window_size); if (!table_ptr) { ACPI_ERROR((AE_INFO, "Could not map memory at 0x%8.8X for length %u", - physical_address, ACPI_EBDA_WINDOW_SIZE)); + physical_address, ebda_window_size)); return_ACPI_STATUS(AE_NO_MEMORY); } mem_rover = - acpi_tb_scan_memory_for_rsdp(table_ptr, - ACPI_EBDA_WINDOW_SIZE); - acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE); + acpi_tb_scan_memory_for_rsdp(table_ptr, ebda_window_size); + acpi_os_unmap_memory(table_ptr, ebda_window_size); if (mem_rover) { |