Commit ee271ddd authored by Gatlin Newhouse's avatar Gatlin Newhouse Committed by Wen Zhiwei
Browse files

x86/traps: Enable UBSAN traps on x86 

stable inclusion
from stable-v6.6.60
commit 86ee1845cbbf52eff6d41ce438d5f7e9ab6f4602
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IB44K1

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=86ee1845cbbf52eff6d41ce438d5f7e9ab6f4602



--------------------------------

[ Upstream commit 7424fc6b86c8980a87169e005f5cd4438d18efe6 ]

Currently ARM64 extracts which specific sanitizer has caused a trap via
encoded data in the trap instruction. Clang on x86 currently encodes the
same data in the UD1 instruction but x86 handle_bug() and
is_valid_bugaddr() currently only look at UD2.

Bring x86 to parity with ARM64, similar to commit 25b84002 ("arm64:
Support Clang UBSAN trap codes for better reporting"). See the llvm
links for information about the code generation.

Enable the reporting of UBSAN sanitizer details on x86 compiled with clang
when CONFIG_UBSAN_TRAP=y by analysing UD1 and retrieving the type immediate
which is encoded by the compiler after the UD1.

[ tglx: Simplified it by moving the printk() into handle_bug() ]

Signed-off-by: default avatarGatlin Newhouse <gatlin.newhouse@gmail.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20240724000206.451425-1-gatlin.newhouse@gmail.com
Link: https://github.com/llvm/llvm-project/commit/c5978f42ec8e9#diff-bb68d7cd885f41cfc35843998b0f9f534adb60b415f647109e597ce448e92d9f
Link: https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/X86/X86InstrSystem.td#L27


Stable-dep-of: 1db272864ff2 ("x86/traps: move kmsan check after instrumentation_begin")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarWen Zhiwei <wenzhiwei@kylinos.cn>
parent 922ac5be

arch/x86/include/asm/bug.h

+12 −0
Original line number Diff line number Diff line
@@ -13,6 +13,18 @@ 
#define INSN_UD2	0x0b0f

#define LEN_UD2		2



/*

 * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit.

 */

#define INSN_ASOP		0x67

#define OPCODE_ESCAPE		0x0f

#define SECOND_BYTE_OPCODE_UD1	0xb9

#define SECOND_BYTE_OPCODE_UD2	0x0b



#define BUG_NONE		0xffff

#define BUG_UD1			0xfffe

#define BUG_UD2			0xfffd



#ifdef CONFIG_GENERIC_BUG



#ifdef CONFIG_X86_32

arch/x86/kernel/traps.c

+54 −5
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ 
#include <linux/hardirq.h>

#include <linux/atomic.h>

#include <linux/iommu.h>

#include <linux/ubsan.h>



#include <asm/stacktrace.h>

#include <asm/processor.h>
@@ -94,6 +95,47 @@ __always_inline int is_valid_bugaddr(unsigned long addr) 
	return *(unsigned short *)addr == INSN_UD2;

}



/*

 * Check for UD1 or UD2, accounting for Address Size Override Prefixes.

 * If it's a UD1, get the ModRM byte to pass along to UBSan.

 */

__always_inline int decode_bug(unsigned long addr, u32 *imm)

{

	u8 v;



	if (addr < TASK_SIZE_MAX)

		return BUG_NONE;



	v = *(u8 *)(addr++);

	if (v == INSN_ASOP)

		v = *(u8 *)(addr++);

	if (v != OPCODE_ESCAPE)

		return BUG_NONE;



	v = *(u8 *)(addr++);

	if (v == SECOND_BYTE_OPCODE_UD2)

		return BUG_UD2;



	if (!IS_ENABLED(CONFIG_UBSAN_TRAP) || v != SECOND_BYTE_OPCODE_UD1)

		return BUG_NONE;



	/* Retrieve the immediate (type value) for the UBSAN UD1 */

	v = *(u8 *)(addr++);

	if (X86_MODRM_RM(v) == 4)

		addr++;



	*imm = 0;

	if (X86_MODRM_MOD(v) == 1)

		*imm = *(u8 *)addr;

	else if (X86_MODRM_MOD(v) == 2)

		*imm = *(u32 *)addr;

	else

		WARN_ONCE(1, "Unexpected MODRM_MOD: %u\n", X86_MODRM_MOD(v));



	return BUG_UD1;

}





static nokprobe_inline int

do_trap_no_signal(struct task_struct *tsk, int trapnr, const char *str,

		  struct pt_regs *regs,	long error_code)
@@ -219,6 +261,8 @@ static inline void handle_invalid_op(struct pt_regs *regs) 
static noinstr bool handle_bug(struct pt_regs *regs)

{

	bool handled = false;

	int ud_type;

	u32 imm;



	/*

	 * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug()
@@ -226,7 +270,8 @@ static noinstr bool handle_bug(struct pt_regs *regs) 
	 * irqentry_enter().

	 */

	kmsan_unpoison_entry_regs(regs);

	if (!is_valid_bugaddr(regs->ip))

	ud_type = decode_bug(regs->ip, &imm);

	if (ud_type == BUG_NONE)

		return handled;



	/*
@@ -239,11 +284,15 @@ static noinstr bool handle_bug(struct pt_regs *regs) 
	 */

	if (regs->flags & X86_EFLAGS_IF)

		raw_local_irq_enable();

	if (ud_type == BUG_UD2) {

		if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN ||

		    handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) {

			regs->ip += LEN_UD2;

			handled = true;

		}

	} else if (IS_ENABLED(CONFIG_UBSAN_TRAP)) {

		pr_crit("%s at %pS\n", report_ubsan_failure(regs, imm), (void *)regs->ip);

	}

	if (regs->flags & X86_EFLAGS_IF)

		raw_local_irq_disable();

	instrumentation_end();

include/linux/ubsan.h

+5 −0
Original line number Diff line number Diff line
@@ -4,6 +4,11 @@ 


#ifdef CONFIG_UBSAN_TRAP

const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type);

#else

static inline const char *report_ubsan_failure(struct pt_regs *regs, u32 check_type)

{

	return NULL;

}

#endif



#endif

lib/Kconfig.ubsan

+2 −2
Original line number Diff line number Diff line
@@ -28,8 +28,8 @@ config UBSAN_TRAP 


	  Also note that selecting Y will cause your kernel to Oops

	  with an "illegal instruction" error with no further details

	  when a UBSAN violation occurs. (Except on arm64, which will

	  report which Sanitizer failed.) This may make it hard to

	  when a UBSAN violation occurs. (Except on arm64 and x86, which

	  will report which Sanitizer failed.) This may make it hard to

	  determine whether an Oops was caused by UBSAN or to figure

	  out the details of a UBSAN violation. It makes the kernel log

	  output less useful for bug reports.