From: Ard Biesheuvel ardb@kernel.org
commit 63056e8b5ebf41d52170e9f5ba1fc83d1855278c upstream.
Hans reports that his mixed mode systems running v5.6-rc1 kernels hit the WARN_ON() in virt_to_phys_or_null_size(), caused by the fact that efi_guid_t objects on the vmap'ed stack happen to be misaligned with respect to their sizes. As a quick (i.e., backportable) fix, copy GUID pointer arguments to the local stack into a buffer that is naturally aligned to its size, so that it is guaranteed to cover only one physical page.
Note that on x86, we cannot rely on the stack pointer being aligned the way the compiler expects, so we need to allocate an 8-byte aligned buffer of sufficient size, and copy the GUID into that buffer at an offset that is aligned to 16 bytes.
Fixes: f6697df36bdf0bf7 ("x86/efi: Prevent mixed mode boot corruption with CONFIG_VMAP_STACK=y") Reported-by: Hans de Goede hdegoede@redhat.com Signed-off-by: Ard Biesheuvel ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Tested-by: Hans de Goede hdegoede@redhat.com Cc: linux-efi@vger.kernel.org Cc: Ingo Molnar mingo@kernel.org Cc: Thomas Gleixner tglx@linutronix.de Link: https://lore.kernel.org/r/20200221084849.26878-2-ardb@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/platform/efi/efi_64.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)
--- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -790,6 +790,8 @@ static efi_status_t efi_thunk_get_variable(efi_char16_t *name, efi_guid_t *vendor, u32 *attr, unsigned long *data_size, void *data) { + u8 buf[24] __aligned(8); + efi_guid_t *vnd = PTR_ALIGN((efi_guid_t *)buf, sizeof(*vnd)); efi_status_t status; u32 phys_name, phys_vendor, phys_attr; u32 phys_data_size, phys_data; @@ -797,8 +799,10 @@ efi_thunk_get_variable(efi_char16_t *nam
spin_lock_irqsave(&efi_runtime_lock, flags);
+ *vnd = *vendor; + phys_data_size = virt_to_phys_or_null(data_size); - phys_vendor = virt_to_phys_or_null(vendor); + phys_vendor = virt_to_phys_or_null(vnd); phys_name = virt_to_phys_or_null_size(name, efi_name_size(name)); phys_attr = virt_to_phys_or_null(attr); phys_data = virt_to_phys_or_null_size(data, *data_size); @@ -815,14 +819,18 @@ static efi_status_t efi_thunk_set_variable(efi_char16_t *name, efi_guid_t *vendor, u32 attr, unsigned long data_size, void *data) { + u8 buf[24] __aligned(8); + efi_guid_t *vnd = PTR_ALIGN((efi_guid_t *)buf, sizeof(*vnd)); u32 phys_name, phys_vendor, phys_data; efi_status_t status; unsigned long flags;
spin_lock_irqsave(&efi_runtime_lock, flags);
+ *vnd = *vendor; + phys_name = virt_to_phys_or_null_size(name, efi_name_size(name)); - phys_vendor = virt_to_phys_or_null(vendor); + phys_vendor = virt_to_phys_or_null(vnd); phys_data = virt_to_phys_or_null_size(data, data_size);
/* If data_size is > sizeof(u32) we've got problems */ @@ -839,6 +847,8 @@ efi_thunk_set_variable_nonblocking(efi_c u32 attr, unsigned long data_size, void *data) { + u8 buf[24] __aligned(8); + efi_guid_t *vnd = PTR_ALIGN((efi_guid_t *)buf, sizeof(*vnd)); u32 phys_name, phys_vendor, phys_data; efi_status_t status; unsigned long flags; @@ -846,8 +856,10 @@ efi_thunk_set_variable_nonblocking(efi_c if (!spin_trylock_irqsave(&efi_runtime_lock, flags)) return EFI_NOT_READY;
+ *vnd = *vendor; + phys_name = virt_to_phys_or_null_size(name, efi_name_size(name)); - phys_vendor = virt_to_phys_or_null(vendor); + phys_vendor = virt_to_phys_or_null(vnd); phys_data = virt_to_phys_or_null_size(data, data_size);
/* If data_size is > sizeof(u32) we've got problems */ @@ -864,14 +876,18 @@ efi_thunk_get_next_variable(unsigned lon efi_char16_t *name, efi_guid_t *vendor) { + u8 buf[24] __aligned(8); + efi_guid_t *vnd = PTR_ALIGN((efi_guid_t *)buf, sizeof(*vnd)); efi_status_t status; u32 phys_name_size, phys_name, phys_vendor; unsigned long flags;
spin_lock_irqsave(&efi_runtime_lock, flags);
+ *vnd = *vendor; + phys_name_size = virt_to_phys_or_null(name_size); - phys_vendor = virt_to_phys_or_null(vendor); + phys_vendor = virt_to_phys_or_null(vnd); phys_name = virt_to_phys_or_null_size(name, *name_size);
status = efi_thunk(get_next_variable, phys_name_size, @@ -879,6 +895,7 @@ efi_thunk_get_next_variable(unsigned lon
spin_unlock_irqrestore(&efi_runtime_lock, flags);
+ *vendor = *vnd; return status; }