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75045f77f7
Currently, most fixups for attempting to access userspace memory are handled using _ASM_EXTABLE, which is also used for various other types of fixups (e.g. safe MSR access, IRET failures, and a bunch of other things). In order to make it possible to add special safety checks to uaccess fixups (in particular, checking whether the fault address is actually in userspace), introduce a new exception table handler ex_handler_uaccess() and wire it up to all the user access fixups (excluding ones that already use _ASM_EXTABLE_EX). Signed-off-by: Jann Horn <jannh@google.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Kees Cook <keescook@chromium.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: kernel-hardening@lists.openwall.com Cc: dvyukov@google.com Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: Borislav Petkov <bp@alien8.de> Link: https://lkml.kernel.org/r/20180828201421.157735-5-jannh@google.com
89 lines
2.2 KiB
C
89 lines
2.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_X86_FUTEX_H
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#define _ASM_X86_FUTEX_H
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#ifdef __KERNEL__
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#include <linux/futex.h>
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#include <linux/uaccess.h>
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#include <asm/asm.h>
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#include <asm/errno.h>
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#include <asm/processor.h>
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#include <asm/smap.h>
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#define __futex_atomic_op1(insn, ret, oldval, uaddr, oparg) \
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asm volatile("\t" ASM_STAC "\n" \
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"1:\t" insn "\n" \
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"2:\t" ASM_CLAC "\n" \
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"\t.section .fixup,\"ax\"\n" \
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"3:\tmov\t%3, %1\n" \
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"\tjmp\t2b\n" \
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"\t.previous\n" \
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_ASM_EXTABLE_UA(1b, 3b) \
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: "=r" (oldval), "=r" (ret), "+m" (*uaddr) \
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: "i" (-EFAULT), "0" (oparg), "1" (0))
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#define __futex_atomic_op2(insn, ret, oldval, uaddr, oparg) \
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asm volatile("\t" ASM_STAC "\n" \
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"1:\tmovl %2, %0\n" \
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"\tmovl\t%0, %3\n" \
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"\t" insn "\n" \
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"2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \
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"\tjnz\t1b\n" \
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"3:\t" ASM_CLAC "\n" \
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"\t.section .fixup,\"ax\"\n" \
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"4:\tmov\t%5, %1\n" \
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"\tjmp\t3b\n" \
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"\t.previous\n" \
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_ASM_EXTABLE_UA(1b, 4b) \
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_ASM_EXTABLE_UA(2b, 4b) \
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: "=&a" (oldval), "=&r" (ret), \
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"+m" (*uaddr), "=&r" (tem) \
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: "r" (oparg), "i" (-EFAULT), "1" (0))
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static inline int arch_futex_atomic_op_inuser(int op, int oparg, int *oval,
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u32 __user *uaddr)
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{
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int oldval = 0, ret, tem;
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pagefault_disable();
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switch (op) {
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case FUTEX_OP_SET:
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__futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ADD:
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__futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval,
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uaddr, oparg);
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break;
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case FUTEX_OP_OR:
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__futex_atomic_op2("orl %4, %3", ret, oldval, uaddr, oparg);
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break;
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case FUTEX_OP_ANDN:
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__futex_atomic_op2("andl %4, %3", ret, oldval, uaddr, ~oparg);
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break;
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case FUTEX_OP_XOR:
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__futex_atomic_op2("xorl %4, %3", ret, oldval, uaddr, oparg);
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break;
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default:
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ret = -ENOSYS;
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}
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pagefault_enable();
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if (!ret)
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*oval = oldval;
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return ret;
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}
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static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
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u32 oldval, u32 newval)
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{
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return user_atomic_cmpxchg_inatomic(uval, uaddr, oldval, newval);
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}
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#endif
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#endif /* _ASM_X86_FUTEX_H */
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