[PATCH 3.16.y-ckt 012/130] arm64/efi: map the entire UEFI vendor string before reading it

[Luis Henriques]

3.16.7-ckt17 -stable review patch.  If anyone has any objections, please let me know.

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

From: Ard Biesheuvel <ard.biesheuvel at linaro.org>

commit f91b1feada0b6f0a4d33648155b3ded2c4e0707e upstream.

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 at linaro.org>
Fixes: f84d02755f5a ("arm64: add EFI runtime services")
Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
[ luis: backported to 3.16: adjusted context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm64/kernel/efi.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
index 6b6bc795f72d..ddc7e78b51d8 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -98,7 +98,7 @@ static int __init uefi_init(void)
 
 	/* Show what we know for posterity */
 	c16 = early_memremap(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];
@@ -113,7 +113,7 @@ static int __init uefi_init(void)
 	if (retval == 0)
 		set_bit(EFI_CONFIG_TABLES, &efi.flags);
 
-	early_memunmap(c16, sizeof(vendor));
+	early_memunmap(c16, sizeof(vendor) * sizeof(efi_char16_t));
 	early_memunmap(efi.systab,  sizeof(efi_system_table_t));
 
 	return retval;