a0f7085f6a
Add support of kernel stack offset randomization while handling syscall, the offset is defaultly limited by KSTACK_OFFSET_MAX(). In order to avoid triggering stack canaries (due to __builtin_alloca()) and slowing down the entry path, use __no_stack_protector attribute to disable stack protector for do_syscall() at function level. With this patch, the REPORT_STACK test show that: `loongarch64 bits of stack entropy: 7` Reviewed-by: Kees Cook <kees@kernel.org> Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
86 lines
2.3 KiB
C
86 lines
2.3 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Author: Hanlu Li <lihanlu@loongson.cn>
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* Huacai Chen <chenhuacai@loongson.cn>
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*
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* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
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*/
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#include <linux/capability.h>
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#include <linux/entry-common.h>
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#include <linux/errno.h>
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#include <linux/linkage.h>
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#include <linux/objtool.h>
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#include <linux/randomize_kstack.h>
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#include <linux/syscalls.h>
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#include <linux/unistd.h>
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#include <asm/asm.h>
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#include <asm/exception.h>
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#include <asm/loongarch.h>
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#include <asm/signal.h>
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#include <asm/switch_to.h>
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#include <asm-generic/syscalls.h>
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#undef __SYSCALL
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#define __SYSCALL(nr, call) [nr] = (call),
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#define __SYSCALL_WITH_COMPAT(nr, native, compat) __SYSCALL(nr, native)
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SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len, unsigned long,
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prot, unsigned long, flags, unsigned long, fd, unsigned long, offset)
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{
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if (offset & ~PAGE_MASK)
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return -EINVAL;
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return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> PAGE_SHIFT);
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}
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void *sys_call_table[__NR_syscalls] = {
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[0 ... __NR_syscalls - 1] = sys_ni_syscall,
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#include <asm/syscall_table_64.h>
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};
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typedef long (*sys_call_fn)(unsigned long, unsigned long,
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unsigned long, unsigned long, unsigned long, unsigned long);
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void noinstr __no_stack_protector do_syscall(struct pt_regs *regs)
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{
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unsigned long nr;
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sys_call_fn syscall_fn;
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nr = regs->regs[11];
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/* Set for syscall restarting */
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if (nr < NR_syscalls)
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regs->regs[0] = nr + 1;
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regs->csr_era += 4;
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regs->orig_a0 = regs->regs[4];
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regs->regs[4] = -ENOSYS;
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nr = syscall_enter_from_user_mode(regs, nr);
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add_random_kstack_offset();
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if (nr < NR_syscalls) {
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syscall_fn = sys_call_table[nr];
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regs->regs[4] = syscall_fn(regs->orig_a0, regs->regs[5], regs->regs[6],
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regs->regs[7], regs->regs[8], regs->regs[9]);
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}
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/*
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* This value will get limited by KSTACK_OFFSET_MAX(), which is 10
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* bits. The actual entropy will be further reduced by the compiler
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* when applying stack alignment constraints: 16-bytes (i.e. 4-bits)
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* aligned, which will remove the 4 low bits from any entropy chosen
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* here.
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*
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* The resulting 6 bits of entropy is seen in SP[9:4].
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*/
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choose_random_kstack_offset(drdtime());
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syscall_exit_to_user_mode(regs);
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}
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#ifdef CONFIG_RANDOMIZE_KSTACK_OFFSET
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STACK_FRAME_NON_STANDARD(do_syscall);
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#endif
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