[PATCH 3.19.y-ckt 096/130] arm64/efi: map the entire UEFI vendor string before reading it

From: Kamal Mostafa
Date: Thu Aug 27 2015 - 18:25:59 EST

3.19.8-ckt6 -stable review patch. If anyone has any objections, please let me know.


From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

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@xxxxxxxxxx>
Fixes: f84d02755f5a ("arm64: add EFI runtime services")
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
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 2bb4347..dabc3f1 100644
--- a/arch/arm64/kernel/efi.c
+++ b/arch/arm64/kernel/efi.c
@@ -100,12 +100,12 @@ 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];
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",

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