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authorAlexander Lobakin <alobakin@pm.me>2021-01-10 14:21:05 +0000
committerThomas Bogendoerfer <tsbogend@alpha.franken.de>2021-01-13 10:59:04 +0100
commit69e976831cd53f9ba304fd20305b2025ecc78eab (patch)
treef7c79532e16b1f1dc788db4bc6b357aec781cb2c /arch
parent698222457465ce343443be81c5512edda86e5914 (diff)
MIPS: relocatable: fix possible boot hangup with KASLR enabled
LLVM-built Linux triggered a boot hangup with KASLR enabled. arch/mips/kernel/relocate.c:get_random_boot() uses linux_banner, which is a string constant, as a random seed, but accesses it as an array of unsigned long (in rotate_xor()). When the address of linux_banner is not aligned to sizeof(long), such access emits unaligned access exception and hangs the kernel. Use PTR_ALIGN() to align input address to sizeof(long) and also align down the input length to prevent possible access-beyond-end. Fixes: 405bc8fd12f5 ("MIPS: Kernel: Implement KASLR using CONFIG_RELOCATABLE") Cc: stable@vger.kernel.org # 4.7+ Signed-off-by: Alexander Lobakin <alobakin@pm.me> Tested-by: Nathan Chancellor <natechancellor@gmail.com> Reviewed-by: Kees Cook <keescook@chromium.org> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Diffstat (limited to 'arch')
-rw-r--r--arch/mips/kernel/relocate.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 47aeb3350a76..0e365b7c742d 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -187,8 +187,14 @@ static int __init relocate_exception_table(long offset)
static inline __init unsigned long rotate_xor(unsigned long hash,
const void *area, size_t size)
{
- size_t i;
- unsigned long *ptr = (unsigned long *)area;
+ const typeof(hash) *ptr = PTR_ALIGN(area, sizeof(hash));
+ size_t diff, i;
+
+ diff = (void *)ptr - area;
+ if (unlikely(size < diff + sizeof(hash)))
+ return hash;
+
+ size = ALIGN_DOWN(size - diff, sizeof(hash));
for (i = 0; i < size / sizeof(hash); i++) {
/* Rotate by odd number of bits and XOR. */