arm64/efi: map the entire UEFI vendor string before reading it

At boot, the UTF-16 UEFI vendor string is copied from the system
table into a char array with a size of 100 bytes. However, this
size of 100 bytes is also used for memremapping() the source,
which may not be sufficient if the vendor string exceeds 50
UTF-16 characters, and the placement of the vendor string inside
a 4 KB page happens to leave the end unmapped.

So use the correct '100 * sizeof(efi_char16_t)' for the size of
the mapping.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Fixes: f84d02755f5a ("arm64: add EFI runtime services")
Cc: <stable@vger.kernel.org> # 3.16+
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 9d4aa18..e8ca6ea 100644 (file)
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -122,12 +122,12 @@ static int __init uefi_init(void)
 
        /* Show what we know for posterity */
        c16 = early_memremap(efi_to_phys(efi.systab->fw_vendor),
-                            sizeof(vendor));
+                            sizeof(vendor) * sizeof(efi_char16_t));
        if (c16) {
                for (i = 0; i < (int) sizeof(vendor) - 1 && *c16; ++i)
                        vendor[i] = c16[i];
                vendor[i] = '\0';
-               early_memunmap(c16, sizeof(vendor));
+               early_memunmap(c16, sizeof(vendor) * sizeof(efi_char16_t));
        }
 
        pr_info("EFI v%u.%.02u by %s\n",