From: Ard Biesheuvel ardb@kernel.org

mainline inclusion from mainline-5.5-rc3 commit ab0eb16205b4 category: bugfix bugzilla: 27656 CVE: NA

-------------------------------------------------

Memory regions that are reserved using efi_mem_reserve_persistent() are recorded in a special EFI config table which survives kexec, allowing the incoming kernel to honour them as well. However, such reservations are not visible in /proc/iomem, and so the kexec tools that load the incoming kernel and its initrd into memory may overwrite these reserved regions before the incoming kernel has a chance to reserve them from further use.

Address this problem by adding these reservations to /proc/iomem as they are created. Note that reservations that are inherited from a previous kernel are memblock_reserve()'d early on, so they are already visible in /proc/iomem.

Tested-by: Masayoshi Mizuma m.mizuma@jp.fujitsu.com Tested-by: Bhupesh Sharma bhsharma@redhat.com Signed-off-by: Ard Biesheuvel ardb@kernel.org Reviewed-by: Bhupesh Sharma bhsharma@redhat.com Cc: stable@vger.kernel.org # v5.4+ Cc: Andy Shevchenko andriy.shevchenko@linux.intel.com Cc: Arvind Sankar nivedita@alum.mit.edu Cc: linux-efi@vger.kernel.org Link: https://lkml.kernel.org/r/20191206165542.31469-2-ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/firmware/efi/efi.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c index e304439..f386a78 100644 --- a/drivers/firmware/efi/efi.c +++ b/drivers/firmware/efi/efi.c @@ -998,6 +998,24 @@ static int __init efi_memreserve_map_root(void) return 0; }

+static int efi_mem_reserve_iomem(phys_addr_t addr, u64 size) +{ + struct resource *res, *parent; + + res = kzalloc(sizeof(struct resource), GFP_ATOMIC); + if (!res) + return -ENOMEM; + + res->name = "reserved"; + res->flags = IORESOURCE_MEM; + res->start = addr; + res->end = addr + size - 1; + + /* we expect a conflict with a 'System RAM' region */ + parent = request_resource_conflict(&iomem_resource, res); + return parent ? request_resource(parent, res) : 0; +} + int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) { struct linux_efi_memreserve *rsv; @@ -1022,7 +1040,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) rsv->entry[index].size = size;

memunmap(rsv); - return 0; + return efi_mem_reserve_iomem(addr, size); } memunmap(rsv); } @@ -1032,6 +1050,12 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) if (!rsv) return -ENOMEM;

+ rc = efi_mem_reserve_iomem(__pa(rsv), SZ_4K); + if (rc) { + free_page((unsigned long)rsv); + return rc; + } + /* * The memremap() call above assumes that a linux_efi_memreserve entry * never crosses a page boundary, so let's ensure that this remains true @@ -1048,7 +1072,7 @@ int __ref efi_mem_reserve_persistent(phys_addr_t addr, u64 size) efi_memreserve_root->next = __pa(rsv); spin_unlock(&efi_mem_reserve_persistent_lock);

- return 0; + return efi_mem_reserve_iomem(addr, size); }

static int __init efi_memreserve_root_init(void)