x86/irq: Make run_on_irqstack_cond() typesafe

Sami reported that run_on_irqstack_cond() requires the caller to cast
functions to mismatching types, which trips indirect call Control-Flow
Integrity (CFI) in Clang.

Instead of disabling CFI on that function, provide proper helpers for
the three call variants. The actual ASM code stays the same as that is
out of reach.

 [ bp: Fix __run_on_irqstack() prototype to match. ]

Fixes: 931b94145981 ("x86/entry: Provide helpers for executing on the irqstack")
Reported-by: Nathan Chancellor <natechancellor@gmail.com>
Reported-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Cc: <stable@vger.kernel.org>
Link: https://github.com/ClangBuiltLinux/linux/issues/1052
Link: https://lkml.kernel.org/r/87pn6eb5tv.fsf@nanos.tec.linutronix.de

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 2f84c7ca74ea970c61b123a9d95f42695aa70a03..870efeec8bdacc2f8d027892198d96c5a54cabd7 100644 (file)
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -299,7 +299,7 @@ __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
        old_regs = set_irq_regs(regs);
 
        instrumentation_begin();
-       run_on_irqstack_cond(__xen_pv_evtchn_do_upcall, NULL, regs);
+       run_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs);
        instrumentation_begin();
 
        set_irq_regs(old_regs);

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 70dea9337816272caf56675f1d5b900554cf3d8b..d977079a7d02e2b92d85d3b9c7545a8969d29d5e 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -682,6 +682,8 @@ SYM_CODE_END(.Lbad_gs)
  * rdx: Function argument (can be NULL if none)
  */
 SYM_FUNC_START(asm_call_on_stack)
+SYM_INNER_LABEL(asm_call_sysvec_on_stack, SYM_L_GLOBAL)
+SYM_INNER_LABEL(asm_call_irq_on_stack, SYM_L_GLOBAL)
        /*
         * Save the frame pointer unconditionally. This allows the ORC
         * unwinder to handle the stack switch.

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index a4336619121208135c18fad12be42d90ba9d603e..a0638640f1edae20c15139a042ae9f45830206bc 100644 (file)
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -242,7 +242,7 @@ __visible noinstr void func(struct pt_regs *regs)                   \
        instrumentation_begin();                                        \
        irq_enter_rcu();                                                \
        kvm_set_cpu_l1tf_flush_l1d();                                   \
-       run_on_irqstack_cond(__##func, regs, regs);                     \
+       run_sysvec_on_irqstack_cond(__##func, regs);                    \
        irq_exit_rcu();                                                 \
        instrumentation_end();                                          \
        irqentry_exit(regs, state);                                     \

diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h
index 4ae66f097101d1cae8c2b23f2f4835fd944e4b56..775816965c6ae098f249dcf83c61d131da0ced9a 100644 (file)
--- a/arch/x86/include/asm/irq_stack.h
+++ b/arch/x86/include/asm/irq_stack.h
@@ -12,20 +12,50 @@ static __always_inline bool irqstack_active(void)
        return __this_cpu_read(irq_count) != -1;
 }
 
-void asm_call_on_stack(void *sp, void *func, void *arg);
+void asm_call_on_stack(void *sp, void (*func)(void), void *arg);
+void asm_call_sysvec_on_stack(void *sp, void (*func)(struct pt_regs *regs),
+                             struct pt_regs *regs);
+void asm_call_irq_on_stack(void *sp, void (*func)(struct irq_desc *desc),
+                          struct irq_desc *desc);
 
-static __always_inline void __run_on_irqstack(void *func, void *arg)
+static __always_inline void __run_on_irqstack(void (*func)(void))
 {
        void *tos = __this_cpu_read(hardirq_stack_ptr);
 
        __this_cpu_add(irq_count, 1);
-       asm_call_on_stack(tos - 8, func, arg);
+       asm_call_on_stack(tos - 8, func, NULL);
+       __this_cpu_sub(irq_count, 1);
+}
+
+static __always_inline void
+__run_sysvec_on_irqstack(void (*func)(struct pt_regs *regs),
+                        struct pt_regs *regs)
+{
+       void *tos = __this_cpu_read(hardirq_stack_ptr);
+
+       __this_cpu_add(irq_count, 1);
+       asm_call_sysvec_on_stack(tos - 8, func, regs);
+       __this_cpu_sub(irq_count, 1);
+}
+
+static __always_inline void
+__run_irq_on_irqstack(void (*func)(struct irq_desc *desc),
+                     struct irq_desc *desc)
+{
+       void *tos = __this_cpu_read(hardirq_stack_ptr);
+
+       __this_cpu_add(irq_count, 1);
+       asm_call_irq_on_stack(tos - 8, func, desc);
        __this_cpu_sub(irq_count, 1);
 }
 
 #else /* CONFIG_X86_64 */
 static inline bool irqstack_active(void) { return false; }
-static inline void __run_on_irqstack(void *func, void *arg) { }
+static inline void __run_on_irqstack(void (*func)(void)) { }
+static inline void __run_sysvec_on_irqstack(void (*func)(struct pt_regs *regs),
+                                           struct pt_regs *regs) { }
+static inline void __run_irq_on_irqstack(void (*func)(struct irq_desc *desc),
+                                        struct irq_desc *desc) { }
 #endif /* !CONFIG_X86_64 */
 
 static __always_inline bool irq_needs_irq_stack(struct pt_regs *regs)
@@ -37,17 +67,40 @@ static __always_inline bool irq_needs_irq_stack(struct pt_regs *regs)
        return !user_mode(regs) && !irqstack_active();
 }
 
-static __always_inline void run_on_irqstack_cond(void *func, void *arg,
+
+static __always_inline void run_on_irqstack_cond(void (*func)(void),
                                                 struct pt_regs *regs)
 {
-       void (*__func)(void *arg) = func;
+       lockdep_assert_irqs_disabled();
+
+       if (irq_needs_irq_stack(regs))
+               __run_on_irqstack(func);
+       else
+               func();
+}
+
+static __always_inline void
+run_sysvec_on_irqstack_cond(void (*func)(struct pt_regs *regs),
+                           struct pt_regs *regs)
+{
+       lockdep_assert_irqs_disabled();
 
+       if (irq_needs_irq_stack(regs))
+               __run_sysvec_on_irqstack(func, regs);
+       else
+               func(regs);
+}
+
+static __always_inline void
+run_irq_on_irqstack_cond(void (*func)(struct irq_desc *desc), struct irq_desc *desc,
+                        struct pt_regs *regs)
+{
        lockdep_assert_irqs_disabled();
 
        if (irq_needs_irq_stack(regs))
-               __run_on_irqstack(__func, arg);
+               __run_irq_on_irqstack(func, desc);
        else
-               __func(arg);
+               func(desc);
 }
 
 #endif

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 181060247e3cb75789d7522b0b0be0d6483c3596..c5dd50369e2f3394bc483b8744ace94eaaea552b 100644 (file)
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -227,7 +227,7 @@ static __always_inline void handle_irq(struct irq_desc *desc,
                                       struct pt_regs *regs)
 {
        if (IS_ENABLED(CONFIG_X86_64))
-               run_on_irqstack_cond(desc->handle_irq, desc, regs);
+               run_irq_on_irqstack_cond(desc->handle_irq, desc, regs);
        else
                __handle_irq(desc, regs);
 }

diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 1b4fe93a86c5ce90cdc2d636dba732e80649ddde..440eed558558d9891547ee1bd09a4570bc398156 100644 (file)
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -74,5 +74,5 @@ int irq_init_percpu_irqstack(unsigned int cpu)
 
 void do_softirq_own_stack(void)
 {
-       run_on_irqstack_cond(__do_softirq, NULL, NULL);
+       run_on_irqstack_cond(__do_softirq, NULL);
 }