From: Alexander Lobakin <alobakin@pm.me>
To: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Nathan Chancellor <natechancellor@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@chromium.org>,
Jinyang He <hejinyang@loongson.cn>,
Alexander Lobakin <alobakin@pm.me>,
Ralf Baechle <ralf@linux-mips.org>,
Matt Redfearn <matt.redfearn@mips.com>,
linux-mips@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: [PATCH mips-fixes] MIPS: relocatable: fix possible boot hangup with KASLR enabled
Date: Sun, 10 Jan 2021 14:21:05 +0000 [thread overview]
Message-ID: <20210110142023.185275-1-alobakin@pm.me> (raw)
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>
---
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 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. */
--
2.30.0
next reply other threads:[~2021-01-10 14:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-10 14:21 Alexander Lobakin [this message]
2021-01-11 5:21 ` [PATCH mips-fixes] MIPS: relocatable: fix possible boot hangup with KASLR enabled Nathan Chancellor
2021-01-11 19:52 ` Kees Cook
2021-01-13 10:43 ` Thomas Bogendoerfer
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