From f7a97dc302bee9d230b1f8823f0f606a21b9de94 Mon Sep 17 00:00:00 2001 From: Alexander Lobakin Date: Sun, 10 Jan 2021 14:21:05 +0000 Subject: [PATCH] MIPS: relocatable: fix possible boot hangup with KASLR enabled commit 69e976831cd53f9ba304fd20305b2025ecc78eab upstream. 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 Tested-by: Nathan Chancellor Reviewed-by: Kees Cook Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/relocate.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c index 3d80a51256de..dab8febb5741 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. */