From: Ard Biesheuvel ardb@kernel.org
[ Upstream commit ffc2760bcf2dba0dbef74013ed73eea8310cc52c ]
Fix a couple of issues with the way we map and copy the vendor string: - we map only 2 bytes, which usually works since you get at least a page, but if the vendor string happens to cross a page boundary, a crash will result - only call early_memunmap() if early_memremap() succeeded, or we will call it with a NULL address which it doesn't like, - while at it, switch to early_memremap_ro(), and array indexing rather than pointer dereferencing to read the CHAR16 characters.
Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Andy Lutomirski luto@kernel.org Cc: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: Arvind Sankar nivedita@alum.mit.edu Cc: Matthew Garrett mjg59@google.com Cc: linux-efi@vger.kernel.org Fixes: 5b83683f32b1 ("x86: EFI runtime service support") Link: https://lkml.kernel.org/r/20200103113953.9571-5-ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/platform/efi/efi.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 38d44f36d5ede..06f69bcd233fe 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -541,7 +541,6 @@ void __init efi_init(void) efi_char16_t *c16; char vendor[100] = "unknown"; int i = 0; - void *tmp;
#ifdef CONFIG_X86_32 if (boot_params.efi_info.efi_systab_hi || @@ -566,14 +565,16 @@ void __init efi_init(void) /* * Show what we know for posterity */ - c16 = tmp = early_memremap(efi.systab->fw_vendor, 2); + c16 = early_memremap_ro(efi.systab->fw_vendor, + sizeof(vendor) * sizeof(efi_char16_t)); if (c16) { - for (i = 0; i < sizeof(vendor) - 1 && *c16; ++i) - vendor[i] = *c16++; + for (i = 0; i < sizeof(vendor) - 1 && c16[i]; ++i) + vendor[i] = c16[i]; vendor[i] = '\0'; - } else + early_memunmap(c16, sizeof(vendor) * sizeof(efi_char16_t)); + } else { pr_err("Could not map the firmware vendor!\n"); - early_memunmap(tmp, 2); + }
pr_info("EFI v%u.%.02u by %s\n", efi.systab->hdr.revision >> 16,