x86/fault: Plumb error code and fault address through to fault handlers

thejh · KAGA-KOKO · commit 81fd9c18444e · 2018-09-03T15:12:09.000+02:00
This is preparation for looking at trap number and fault address in the handlers for uaccess errors. No functional change. 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: linux-kernel@vger.kernel.org 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/20180828201421.157735-6-jannh@google.com
diff --git a/arch/x86/include/asm/extable.h b/arch/x86/include/asm/extable.h
@@ -29,7 +29,8 @@ struct pt_regs;
 		(b)->handler = (tmp).handler - (delta);		\
 	} while (0)
 
-extern int fixup_exception(struct pt_regs *regs, int trapnr);
+extern int fixup_exception(struct pt_regs *regs, int trapnr,
+			   unsigned long error_code, unsigned long fault_addr);
 extern int fixup_bug(struct pt_regs *regs, int trapnr);
 extern bool ex_has_fault_handler(unsigned long ip);
 extern void early_fixup_exception(struct pt_regs *regs, int trapnr);
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
@@ -37,8 +37,10 @@ struct pt_regs {
 	unsigned short __esh;
 	unsigned short fs;
 	unsigned short __fsh;
+	/* On interrupt, gs and __gsh store the vector number. */
 	unsigned short gs;
 	unsigned short __gsh;
+	/* On interrupt, this is the error code. */
 	unsigned long orig_ax;
 	unsigned long ip;
 	unsigned short cs;
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1315,7 +1315,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 		local_irq_disable();
 		ist_end_non_atomic();
 	} else {
-		if (!fixup_exception(regs, X86_TRAP_MC))
+		if (!fixup_exception(regs, X86_TRAP_MC, error_code, 0))
 			mce_panic("Failed kernel mode recovery", &m, NULL);
 	}
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
@@ -206,7 +206,7 @@ do_trap_no_signal(struct task_struct *tsk, int trapnr, char *str,
 	}
 
 	if (!user_mode(regs)) {
-		if (fixup_exception(regs, trapnr))
+		if (fixup_exception(regs, trapnr, error_code, 0))
 			return 0;
 
 		tsk->thread.error_code = error_code;
@@ -551,7 +551,7 @@ do_general_protection(struct pt_regs *regs, long error_code)
 
 	tsk = current;
 	if (!user_mode(regs)) {
-		if (fixup_exception(regs, X86_TRAP_GP))
+		if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
 			return;
 
 		tsk->thread.error_code = error_code;
@@ -848,7 +848,7 @@ static void math_error(struct pt_regs *regs, int error_code, int trapnr)
 	cond_local_irq_enable(regs);
 
 	if (!user_mode(regs)) {
-		if (fixup_exception(regs, trapnr))
+		if (fixup_exception(regs, trapnr, error_code, 0))
 			return;
 
 		task->thread.error_code = error_code;
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
@@ -8,7 +8,8 @@
 #include <asm/kdebug.h>
 
 typedef bool (*ex_handler_t)(const struct exception_table_entry *,
-			    struct pt_regs *, int);
+			    struct pt_regs *, int, unsigned long,
+			    unsigned long);
 
 static inline unsigned long
 ex_fixup_addr(const struct exception_table_entry *x)
@@ -22,15 +23,19 @@ ex_fixup_handler(const struct exception_table_entry *x)
 }
 
 __visible bool ex_handler_default(const struct exception_table_entry *fixup,
-				  struct pt_regs *regs, int trapnr)
+				  struct pt_regs *regs, int trapnr,
+				  unsigned long error_code,
+				  unsigned long fault_addr)
 {
 	regs->ip = ex_fixup_addr(fixup);
 	return true;
 }
 EXPORT_SYMBOL(ex_handler_default);
 
 __visible bool ex_handler_fault(const struct exception_table_entry *fixup,
-				struct pt_regs *regs, int trapnr)
+				struct pt_regs *regs, int trapnr,
+				unsigned long error_code,
+				unsigned long fault_addr)
 {
 	regs->ip = ex_fixup_addr(fixup);
 	regs->ax = trapnr;
@@ -43,7 +48,9 @@ EXPORT_SYMBOL_GPL(ex_handler_fault);
  * result of a refcount inc/dec/add/sub.
  */
 __visible bool ex_handler_refcount(const struct exception_table_entry *fixup,
-				   struct pt_regs *regs, int trapnr)
+				   struct pt_regs *regs, int trapnr,
+				   unsigned long error_code,
+				   unsigned long fault_addr)
 {
 	/* First unconditionally saturate the refcount. */
 	*(int *)regs->cx = INT_MIN / 2;
@@ -96,7 +103,9 @@ EXPORT_SYMBOL(ex_handler_refcount);
  * out all the FPU registers) if we can't restore from the task's FPU state.
  */
 __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
-				    struct pt_regs *regs, int trapnr)
+				    struct pt_regs *regs, int trapnr,
+				    unsigned long error_code,
+				    unsigned long fault_addr)
 {
 	regs->ip = ex_fixup_addr(fixup);
 
@@ -109,15 +118,19 @@ __visible bool ex_handler_fprestore(const struct exception_table_entry *fixup,
 EXPORT_SYMBOL_GPL(ex_handler_fprestore);
 
 __visible bool ex_handler_uaccess(const struct exception_table_entry *fixup,
-				  struct pt_regs *regs, int trapnr)
+				  struct pt_regs *regs, int trapnr,
+				  unsigned long error_code,
+				  unsigned long fault_addr)
 {
 	regs->ip = ex_fixup_addr(fixup);
 	return true;
 }
 EXPORT_SYMBOL(ex_handler_uaccess);
 
 __visible bool ex_handler_ext(const struct exception_table_entry *fixup,
-			      struct pt_regs *regs, int trapnr)
+			      struct pt_regs *regs, int trapnr,
+			      unsigned long error_code,
+			      unsigned long fault_addr)
 {
 	/* Special hack for uaccess_err */
 	current->thread.uaccess_err = 1;
@@ -127,7 +140,9 @@ __visible bool ex_handler_ext(const struct exception_table_entry *fixup,
 EXPORT_SYMBOL(ex_handler_ext);
 
 __visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup,
-				       struct pt_regs *regs, int trapnr)
+				       struct pt_regs *regs, int trapnr,
+				       unsigned long error_code,
+				       unsigned long fault_addr)
 {
 	if (pr_warn_once("unchecked MSR access error: RDMSR from 0x%x at rIP: 0x%lx (%pF)\n",
 			 (unsigned int)regs->cx, regs->ip, (void *)regs->ip))
@@ -142,7 +157,9 @@ __visible bool ex_handler_rdmsr_unsafe(const struct exception_table_entry *fixup
 EXPORT_SYMBOL(ex_handler_rdmsr_unsafe);
 
 __visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup,
-				       struct pt_regs *regs, int trapnr)
+				       struct pt_regs *regs, int trapnr,
+				       unsigned long error_code,
+				       unsigned long fault_addr)
 {
 	if (pr_warn_once("unchecked MSR access error: WRMSR to 0x%x (tried to write 0x%08x%08x) at rIP: 0x%lx (%pF)\n",
 			 (unsigned int)regs->cx, (unsigned int)regs->dx,
@@ -156,12 +173,14 @@ __visible bool ex_handler_wrmsr_unsafe(const struct exception_table_entry *fixup
 EXPORT_SYMBOL(ex_handler_wrmsr_unsafe);
 
 __visible bool ex_handler_clear_fs(const struct exception_table_entry *fixup,
-				   struct pt_regs *regs, int trapnr)
+				   struct pt_regs *regs, int trapnr,
+				   unsigned long error_code,
+				   unsigned long fault_addr)
 {
 	if (static_cpu_has(X86_BUG_NULL_SEG))
 		asm volatile ("mov %0, %%fs" : : "rm" (__USER_DS));
 	asm volatile ("mov %0, %%fs" : : "rm" (0));
-	return ex_handler_default(fixup, regs, trapnr);
+	return ex_handler_default(fixup, regs, trapnr, error_code, fault_addr);
 }
 EXPORT_SYMBOL(ex_handler_clear_fs);
 
@@ -178,7 +197,8 @@ __visible bool ex_has_fault_handler(unsigned long ip)
 	return handler == ex_handler_fault;
 }
 
-int fixup_exception(struct pt_regs *regs, int trapnr)
+int fixup_exception(struct pt_regs *regs, int trapnr, unsigned long error_code,
+		    unsigned long fault_addr)
 {
 	const struct exception_table_entry *e;
 	ex_handler_t handler;
@@ -202,7 +222,7 @@ int fixup_exception(struct pt_regs *regs, int trapnr)
 		return 0;
 
 	handler = ex_fixup_handler(e);
-	return handler(e, regs, trapnr);
+	return handler(e, regs, trapnr, error_code, fault_addr);
 }
 
 extern unsigned int early_recursion_flag;
@@ -238,9 +258,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
 	 * result in a hard-to-debug panic.
 	 *
 	 * Keep in mind that not all vectors actually get here.  Early
-	 * fage faults, for example, are special.
+	 * page faults, for example, are special.
 	 */
-	if (fixup_exception(regs, trapnr))
+	if (fixup_exception(regs, trapnr, regs->orig_ax, 0))
 		return;
 
 	if (fixup_bug(regs, trapnr))
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
@@ -711,7 +711,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
 	int sig;
 
 	/* Are we prepared to handle this kernel fault? */
-	if (fixup_exception(regs, X86_TRAP_PF)) {
+	if (fixup_exception(regs, X86_TRAP_PF, error_code, address)) {
 		/*
 		 * Any interrupt that takes a fault gets the fixup. This makes
 		 * the below recursive fault logic only apply to a faults from

Original file line number	Diff line number	Diff line change
`@@ -1315,7 +1315,7 @@ void do_machine_check(struct pt_regs *regs, long error_code)`
`1315`	`1315`	`local_irq_disable();`
`1316`	`1316`	`ist_end_non_atomic();`
`1317`	`1317`	`} else {`
`1318`		`- if (!fixup_exception(regs, X86_TRAP_MC))`
	`1318`	`+ if (!fixup_exception(regs, X86_TRAP_MC, error_code, 0))`
`1319`	`1319`	`mce_panic("Failed kernel mode recovery", &m, NULL);`
`1320`	`1320`	`}`
`1321`	`1321`